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FIRST PRINCIPLES 
OF son, FERTILin 



By 
ALFRED VIVIAN 

Professor of Agricultural Chemistry in the College of Apiculture 
of the Ohio State University 



ILLUSTRATED 



NEW YORK 

ORANGE JUDD COMPANY 

LONDON 
KEGAN PAUL, TRENCH, TRUBNER & CO., Limited 

1908 



^^ 






LIBRARY Of CONGRESS 

Two O«0ies KecdivaG 

JAN 14 1908 



CLASS 4 'XXC. No. 

1 '"?C»«^'? 



OOFY a. 



Copyright 1908 by 

ORANGE JUDD COMPANY 

All Rights Reserved 



Entered at Stationers' Hall, London. England 



"Ye rigid Ploughmen!, bear, in mind. . 
Your labor is for future hours. 
Advance ! spare not ! nor look behind 1 

Plough deep and straight with all your powers! " 

Richard Hengist Horne. 



"When tillage begins, other arts follow. The farmers 
therefore, are the founders of human civilization." 

Daniel Webster. 



ACKNOWLEDGMENTS 



The author desires to acknowledge his obligation to the 
following named persons for the illustrations found on 
the pages indicated: Director C. E. Thorne, Ohio Experi- 
ment Station, 182, 230, 250; Director J. H. Stewart, West 
Virginia Experiment Station, 112, 176, 177; Director H. J. 
Wheeler, Rhode Island Experiment Station, 246, 248; Pres- 
ident A. M. Soule, North Georgia Agricultural College, 
formerly Director Tennessee Experiment Station, 206, 216, 
217; Director L. H. Bailey, Cornell Experiment Station, 
187, 205; Professor F. H. King, Madison, Wisconsin, 62; 
L. H. Goddard, Ohio Experiment Station, 147, 243, 245; 
Professor V. H. Davis, Ohio State University, 103; Pro- 
fessor W. J. Frazer, University of Illinois, 159; F. H. Has- 
kett, Columbus, Ohio, 28, 29, and frontispiece; Orange 
Judd Company, 4, 39, 89, 120, 218. The line drawings are 
by Orange Judd Company's artist, Mr. B. F. Williamson. 
Credit for the remaining illustrations, where not cited, is 
equally divided between Mr. A. B. Graham, Superintendent 
of Agricultural Extension, Ohio State University, and the 
author. 



PREFACE 



This little book is intended primarily for home read- 
ing. It is written, however, largely from lecture notes 
used by the author in a course in soil fertility given to 
winter course students, and, therefore, will be found 
to be a suitable text for short courses. It is an at- 
tempt to present in non-technical language a subject 
of great scientific and practical interest to the farmer. 
The subject of Soil Fertility is so large, that each 
phase of it could of necessity be only briefly considered 
in a small book, and the writer did not pretend to 
make the discussion of any topic exhaustive. For this 
reason some things have been omitted which might 
have been discussed with profit in a larger work. Only 
the more important facts concerning the maintenance 
of fertility have been presented, but it is believed that 
the statements so far as they go are in accord with 
the best scientific thought and practice of the day. 

A certain amount of repetition has been purposely 
used in the text ; for it is felt that in this way only 
can the more important facts be given the emphasis 
which they deserve, but it is thought that this method 
of treatment has not been carried to the point of mo- 
notony. It is hoped that this book may find a little 
place in agricultural literature which is not already 
filled, and that it may be the means of leading a few 
earnest minds to a more extended study of this im- 
portant subject of the fertility of the soil. 

Alfred Vivian. 

Ohio State Uiiii'crsitv. 

Columbus, Ohio. 



CONTENTS 



CHAPTER PAGE 

I. Introductory 3 

II. Atmosphere as a Source of Plant Food . . 12 

III. Nitrogen as a Plant Food 21 

IV. Soil as a Source of Plant Food 31 

V. Origin of the Soil 47 

VI. Tillage 63 

VII. Drainage and Irrigation 75 

VIII. Summer Fallowing 85 

IX. Humus and Green-manuring 94 

X. Rotation of Crops 105 

XI. Factors Affecting Value of Fresh Manure . 113 
XII. Amount and Value of Manure produced on 

Farm 127 

XIII. Losses in Manure I37 

XIV. Preservation of Manure 150 

XV. Applying Manure 165 

XVI. Barnyard Manure and the Maintenance of 

Fertility I73 

XVII. Commercial Fertilizers — Nitrogen .... 185 

XVIII. Potash and Phosphate Fertilizers .... 197 

XIX. Mixed Fertilizers 209 

XX. Using Commercial Fertilizers 219 

XXI. Buying Commercial Fertilizers 233 

XXII. Indirect Fertilizers .......... 242 



PART I 
PLANT FOOD— ITS NATURE AND SOURCE 



CHAPTER I 

INTRODUCTORY 

Farming is a business, and the successful farmer 
must be first of all a business man. He follows his 
vocation primarily for the money he can make, and 
like other business men should aim to get the greatest 
possible returns for the money and labor involved. It 
is not enough simply to grow crops, but they must be 
so produced as to yield a profit on the capital invested. 
To succeed, he must be thoroughly acquainted with 
every detail of his occupation, and must strive to stop 
all leaks and prevent needless waste. At the same 
time, he must bear in mind that it is a good business 
principle to spend a dollar whenever he can see that 
it will come back to him with interest. 

Agriculture is not merely a business but an art as 
well : the art of producing plants and animals that are 
useful to man. A real knowledge of farming neces- 
sitates a knowledge of the principles upon which the 
art of agriculture is founded; for an understanding 
of these principles is essential to an intelligent and 
rational practice. A few years since, "anyone could 
be a farmer." It was only necessary to sow and reap, 
for Nature dealt lavishly with man, and gave to him 
freely of the fertility she had been storing up for count- 
less ages. A system of extravagant and unbusiness- 
like farming, however, has so impoverished the soil, 

3 



4 FIRST PRINCIPLES OF SOIL FERTILITY 

in some parts of our country, that many farms are 
already abandoned, having ceased to be profitable ; and 
that too, in localities where the land once commanded 
high prices. This fact is the more lamentable, because 
the exhaustion of the soil might have been prevented 
by an intelligent foresight on the part of our earlier 
farmers. The farming of the future, therefore, must 
be done by men of broad training which should in- 




An abandoned farm. Many farms have been abandoned because the soil is said 
to be exhausted. This exhaustion of the soil might have been prevented and 
the soils in many cases can be restored to their original fertility. 

elude, among other things, some knowledge of such 
sciences as geology, chemistry, botany, zoology and 
physics. These sciences have done much to explain 
how the fertility of the land may be conserved, and it 
is the aim of this little book to present in a brief man- 
ner the latest views of agricultural investigators and 
farmers on this important subject. The intention is to 
make the treatment of the subject thoroughly practical, 
and for this reason the minimum of theory and the 
maximum of demonstrated facts will be given, and 



INTRODUCTORY 5 

with the least possible use of technical language. Be- 
fore taking up the subject of manures and fertilizers 
it is desirable to devote a short time to the considera- 
tion of plant food in general, explaining what it is and 
its source of supply. 

Plants of First Importance to the Farmer. — All 
agriculture depends upon the growth of plants, and 



^^^i^uMt 



Plants are of first importance to agriculture, The production of animals and 
animal products is merely one way of marketing the crop 



consequently the profit that accrues to the farmer de- 
pends primarily upon the value of the crops his farm 
produces. In some kinds of farming the profit comes 
from the sale of crops that are useful in providing 
food, fuel, or raiment for man, while in others the 
direct gain comes from the sale of animals or animal 
products. Even in the latter case the feeding crops 
that can be grown upon the farm determine its earning 



6 FIRST PRINCIPLES OF SOIL FERTILITY 

power, for the sale of animal products is simply an 
indirect method of marketing the crops. 

The profit from the farm is dependent not only upon 
the total crop produced but also, and to perhaps a still 
larger degree, upon the yield per acre. It stands to 
reason that if the crops now produced on two hundred 
acres could be grown upon one hundred, the returns 
would be greater, provided the labor and other expense 
involved were not materially increased ; for in the 
latter case the interest on the money invested in one 
hundred acres of land would be clear gain. On the 
other hand, it is apparent that nothing is gained by 
increased production per acre if the larger crop is ob- 
tained at a total expenditure in excess of that required 
for the smaller yield. As a matter of fact, our most 
successful farmers have demonstrated that the present 
average of crops can be doubled, and that at a cost per 
acre scarcely more than is now required for the half- 
crop. To accomplish this necessitates a broader knowl- 
edge of the food requirements of plants than is pos- 
sessed by the majority of our farmers. This knowl- 
edge being fundamental, it seems strange that more 
efforts have not been made to acquire it by those 
vitally interested. Strange as it may seem, it is a fact 
that while he has reasonably clear ideas on feeds for 
animals, the average farmer has only very vague and 
often false notions on the subject of plant food and 
plant nutrition. A thorough understanding of these 
subjects on the part of our forerunners in agriculture 
would have rendered it unnecessary to deal with the 
matter considered in the next paragraph. 

Exhaustion of the Soil. — It is a matter of common 



INTRODUCTORY 7 

experience that continued cropping results in a loss 
of fertility. The experiences of the older sections of 
our country teach some lessons by which the newer 
parts may profit. In the beginning the productiveness 
of the rich virgin soil seemed unlimited. For years 
large crops were produced with apparently no decrease 
in fertility. Sooner or later, however, the crops began 
to diminish in size, gradually, to be sure, but unceas- 
ingly, until at last the yield became so small that it no 
longer paid for the cost and labor of cultivation. This 
state of affairs came about more rapidly if the same 
crop was grown continuously on the same field, as was 
often done with wheat. The soil was now said to be 
exhausted, and in many cases the farms were aban- 
doned. An exhausted soil in this sense means one 
that will no longer yield profitable returns, and not 
necessarily one that will produce no crop. As a matter 
of fact a soil can not become exhausted, if by ex- 
haustion we mean total inability to produce a crop. 

At the experiment station at Rothamsted, England, 
barley grown continuously on the same plot for forty- 
three years without the use of fertilizers of any kind 
yielded in the forty-third year lo bushels of dressed 
grain per acre; the average for the last eight years 
being ii^ bushels. Wheat grown in the same way 
for fifty years produced in the fiftieth year 9^ bushels 
of grain per acre ; the average for the last eight years 
being 11^ bushels. In these cases the soil seems 
capable of keeping up the yield indefinitely, as the 
average for the last twenty years is practically the 
same as the average given above for the last eight 
years. 



8 FIRST PRINCIPLES OF SOIL FERTILITY 

While these facts indicate that the soil can never be 
completely exhausted, it is exhausted for all practical 
purposes when the crop produced ceases to be profita- 
ble. The first question that naturally suggests itself is, 
Why does the productive power of the soil diminish? 

The Plant Removes Something from the Soil. — 
It is evident that the virgin land must have contained 
large quantities of some substance or substances that 
were necessary to vigorous plant growth and that these 
materials were removed from the soil when the crop 
was harvested. It is not possible to explain the rapid 
decrease in fertility on any other basis ; for it can not 
be ascribed to any changes in climatic conditions. The 
change in the physical condition of the soil has been 
suggested as a possible explanation for its decreased 
productive power, but even this is not an adequate ex- 
planation. It is apparent also, that plants vary in their 
power to extract these substances from the soil ; for it 
is well known that a soil may be unfertile for one class 
of plants and still produce a luxuriant growth of an- 
other. To ascertain what these materials are that the 
plant removes from the soil, it is necessary to analyze 
the plant and then to determine the sources of the 
ingredients found there. For the purpose of this study 
the corn, or maize, plant is chosen, as it is perhaps the 
most important of all plants to the American farmer. 
Before presenting the analysis it is advisable to devote 
a moment to a few preliminary considerations. 

Elements and Compounds. — Chemistry teaches that 
all matter is composed of simple substances called ele- 
ments. Between 70 and 80 of them are known. They 
are called elements because they are the simplest sub- 



INTRODUCTORY 9 

stances known, and can not by any means yet dis- 
covered, be separated into simpler or different sub- 
stances. Iron, gold, silver and sulphur are examples of 
elements. Two others, both gases (i. e. oxygen and 
nitrogen) make up the bulk of the air. 

Most materials with which we are familiar are com- 
plex and are combinations of two or more elements. 
Such bodies are called compounds. While the number 
of elements is small there are many thousands of com- 
pounds. This is due to the fact that the same elements 
can combine in many different ways, each combination 
forming a different compound. Alcohol, sugar, starch, 
fats and acetic acid, for example, are substances very 
unlike in their properties and yet all consist of the three 
elements carbon, hydrogen and oxygen, but these ele- 
ments are present in different proportions. Plants are 
composed of a large number of compounds, and an 
ideal analysis would first separate the plant into its 
compounds and then these compounds into the elements 
of which they are composed. Approximately such an 
analysis can be made. 

Chemical Composition of the Corn Plant.— If a 
quantity of green corn is allowed to wilt in the sun it 
loses a large percentage of its weight by the evapora- 
tion of the water which it contains. If the remainder 
is now heated in an oven at 212° F. it again decreases 
in weight, but finally reaches a point where the weight 
does not change, because all the water is driven off. 
Water is composed of the two elements hydrogen and 
oxygen. What remains after expelling the water is 
called the dry matter of the plant. The dry matter 
burns on being ignited and a very small amount of 



lO FIRST PRINCIPLES OF SOIL FERTILITY 

mineral matter remains, which is called ash. The part 
that burned, and completely disappeared is known as 
organic matter. The organic matter is composed of 
four classes of compounds known as fat, crude fiber, 
carbohydrates and protein. The first three of these 
compounds are made up of the elements carbon, oxygen 
and hydrogen; and the protein contains in addition to 




Corn or mai^>3 13 one of the most important crops for the American farmer. 
It removes large quantities of plant food from the soil, however. The 
analysis of the corn plant is given on page 1 1 . 

these the element nitrogen. The ash contains the ele- 
ments' potassium, phosphorus, calcium, magnesium, 
iron, sulphur, chlorine, sodium and silicon. The fol- 
lowing table shows the ingredients found in i,ooo 
pounds of the matured corn plant, i. c. when the 
plant is in condition to be cut for shocking. 

From what has been said it will be seen that of the 
elements known only thirteen are found in plants ; for 
what is true of the corn plant holds true of all other 
plants. It will be shown that of these thirteen, three 
are probably not necessary to plant growth, leaving 
only ten elements that are essential. The table shows 



INTRODUCTORY 



II 



that three elements (i. c. hydrogen, oxygen and car- 
bon) make up 98^ per, cent of the entire composition 
of the plant, the remaining elements constituting only 
i>2 per cent. 



COMPOSITION OF THE CORN PLANT 



CORN 
PLANT 
1,000 lbs. 



r Water 

793 



j Ilydfogen 88.1 
i Oxygen 704.9 



Dry 
Matter 

207 



Organic 

Matter 

195 



18. 



Ash 12 



Protein 
Fat 5. 
Fiber 50. 
Carbohydrates \22. 

Chlorine 0.4 
Potash 4.0 
Pnosphoric Acid 1.2 
Lime 1.6 
Magnesia 1.4 
Iron Oxide 0.3 
Sulphuric Acid 0.3 
Soda 0.4 
Silica 2.4 



r Nitrogen 2.9 
I Carbon 90.5 
I Oxygen 88.9 
I Hydrogen 12.7 



(Note. — All of the elements mentioned above as occurring in the 
ash, with the exception of chlorine, are combined with oxygen. In the 
table the names under "ash" represent these combinations, i. c. potash 
is composed of potassium and oxygen; phosphoric acid is phosphorus 
and oxygen; lime is calcium and oxygen, etc.) 



CHAPTER II 

ATMOSPHERE AS A SOURCE OF PLANT 
FOOD 

Importance of Water to the Plant. — One of the 

most striking points brought out by the chemical ana- 
lysis is the large proportion of water that enters into 
the composition of the plant. A reference to the table 
shows that nearly 800 of the 1,000 pounds of the 
matured corn plant consist of water in a form that can 
be driven off at a heat not above the boiling point. 
In the organic matter is found 12.7 pounds of hydrogen 
and 88.9 pounds of oxygen which practically all came 
originally from water, making a total of nearly 900 
pounds derived from this source. These figures re- 
present but a small part of the water actually required 
by the crop. Water is being continually given off into 
the air by the plant-leaves. This exhaled, or *'trans- 
pired," water is in the form of a vapor and is invisible, 
but that it actually exists can be proved by a simple 
experiment. 

Invert a wide mouthed bottle or fruit jar over a 
small plant, and after a short time the inner surface 
of the bottle will be found to be covered with moisture. 
The earth around the plant should first be covered with 
a piece of oil cloth or oiled paper to make sure that the 
water does not come from the soil. If the underside 
of a leaf is examined with a magnifying glass or mi- 
croscope it will be found that the surface is not entire, 

12 



ATMOSPHERE AS A SOURCE OF PLANT FOOD 



13 




but is perforated by numerous small openings. These 
Openings are called ''stomata" (little mouths), and it 
is through these that the water is exhaled. This power 
of transpiration continues during the life of the plant, 
the water being ob- 
t a i n e d from the 
ground through the 
roots. Very large 
quantities of water are 
used in this way. 

Amount of Water 
Required by Crops. 
— European experi- 
ments have shown 
that approximately 
300 pounds of water 
passes through the 
plant for each pound 
of dry matter pro- 
duced, so that 1,000 
pounds of corn use at 
least 30 tons of water 

during its growing period. As this quantity of corn 
can be raised on one-thirtieth of an acre, it follows 
that to mature an acre of corn the crop must be sup- 
plied with 900 tons of water, or an amount that would 
make a layer over the acre about 8 inches deep. 

This again takes no account of the quantity of water 
lost from the land by percolation or drainage. It has 
been estimated that this amount is at least equal to 
that used by vegetation, so that one acre of corn pro- 
bably requires a precipitation of at least 1,800 tons of 



Experiment to show that water is given off 
from the leaves of plants. The bottle on 
the left has been over the plant for some 
time and is cloudy from the moisture which 
has collected on the inside. The one on 
the right has just been placed over the 
plant and is transparent. 

(Drawn from photograph) 



14 FIRST PRINCIPLES OF SOIL FERTILITY 

water. These statements show clearly the necessity of 
carefully conserving the moisture of the soil, a point 
that can not be too strongly emphasized. 

King found in investigations made at Wisconsin that 
the amount of water used by the crop was from 300 to 
500 times the weight of the dry matter. His results 
are summarized in the following table. 

AVERAGE AMOUNT OF WATER USED TO PRODUCE ONE TON 
OF DRY MATTER 

Tons of water for 
Crop grown one ton dry matter 

Barley 461. i 

Oats 503.9 

Corn 270.9 

Clover 576.6 

Peas 477.2 

Potatoes 385.1 

From this and other data he calculated the minimum 
amount of available water necessary to produce the 
various yields of the more common grain crops. These 
interesting figures are given below. 

LEAST AMOUNT OF WATER PER ACRE REQUIRED TO PRO- 
DUCE DIFFERENT YIELDS OF GRAIN 

Yield Acre Inches of Water Required 

per acre Wheat Barley Oats Corn 

15 
20 
30 
40 
50 
60 



4-5 


324 


2.35 


2.52 


6.0 


4.28 


3-14 


3.36 


9.0 


6.42 


57 


5-04 


2.0 


8.56 


6.27 


6.72 


5-0 


10.70 


7.84 


8.40 


8.0 


12.84 


9.40 


10.08 



ATMOSPHERE AS A SOURCE OF PLANT FOOD 1 5 

Functions of Water. — Water is important to the 
plant in several different ways. It is first of all the 
most essential plant food, in the sense that it composes 
about 80 per cent of the mature crop. It also supplies 
the hydrogen and oxygen found in the dry matter, 
which amounts to lo per cent more, making a total of 
90 per cent of the weight of the plant which is derived 
directly from the water. 

Water is necessary to dissolve the plant food in the 
ground, and enable it to enter the plant, as will be 
noted later. It is needed to give stiffness or rigidity 
to the more succulent parts of the plant. This fact is 
shown by the drooping or wilting of plants during the 
hot hours of the day when the water is not furnished 
by the roots with sufficient rapidity to replace the loss 
by evaporation from the leaves. It is probable that 
water performs an important function in controlling 
the temperature of the plant. The chemical processes 
in the plant cells produce heat, and the excess of heat 
is removed by transpiration of water through the 
leaves, just as it is removed from the human body by 
the transpiration (perspiration so-called) through the 
skin. Water is also necessary for the nfovement of food 
within the plant. The food materials absorbed by the 
roots, and that manufactured by the leaves can be trans- 
ported to the different parts of the plant where they 
are needed only when in solution in water. 

Of such consequence to vegetation is the w^ater sup- 
ply that some investigators claim that the question of 
fertility is wholly one of having present in the ground 
the proper amount of moisture, and that it is indepen- 
dent of the chemical composition of the soil, except as 



l6 FIRST PRINCIPLES OF SOIL FERTILITY 

this composition affects its power to furnish the plant 
with water. This view is undoubtedly extreme, and 
is not generally accepted. There is no doubt, how- 
ever, that the proper condition of moisture is the most 
important single factor in determining the fertility of 
the land, and that more soils fail to produce good crops 
for lack of it than for any other cause. It seldom 
happens that the water supply is sufficient to grow the 
maximum crop of which the soil is capable, as is de- 
monstrated by the fact that a large increase in yield can 
be obtained by irrigation even in sections of very heavy 
precipitation. While the amount of water that falls on 
the land can not be controlled, much can be done to save 
the water so as to tide over the periods of scanty rain- 
fall; a fact that will be emphasized throughout this 
book. Too much stress can not be laid upon the im- 
portance to the plant of an adequate supply of water 
in the soil, and the knowledge that certain methods 
increase the amount of moisture available to the crop 
should be sufficient reason for their adoption. The 
reader is asked to carry this thought with him as he 
reads the following pages. 

Part of the Oxygen from the Air. — A small quan- 
tity of the oxygen in the plant probably comes from 
the air. One-fifth of the volume of the air is oxygen, 
and the plant uses this to some extent. Plants breathe 
in much the same manner that animals do, for all cells 
must have a supply of oxygen in order to live. The 
oxygen of the air combines with the materials in the 
cells one of the resuUs being the production of heat, 
just as the oxidaltion taking place in the animal body 
produces ilieat, T^^at heat is evolved by the living 



ATMOSPHERE AS A SOURCE OF PLANT FOOD 1/ 

vegetable cell can easily be proved experimentally by 
confining the plant in such a way as to prevent radia- 
tion. The rapid heating of silage in the silo is doubt- 
less due to the breathing process of the cell, the heat 
in this case being unable to escape. 

Carbon in Plants Derived from the Air. — Nearly 
one-half of the dry matter in the ])lant consists of the 
element carbon, all of which is derived from the car- 
bonic acid gas which is present in the atmosphere. 
Carbonic acid is the colorless gas which is formed when 
a piece of coal or charcoal is burned, and is a com- 
pound containing the two elements carbon and oxygen. 
Charcoal is a good exami)le of nearly pure carbon. 
Carbonic acid gas is found everywhere in the atmo- 
sphere, although present in very small quantities, con- 
stituting only four one-hundredths of one per cent of 
the volume of the air, or about four parts in 10,000. 
It seems strange to think that so large a proportion of 
the solid material of the plant should be formed from 
this gas, but it is well known that green plants have 
the i)ower to decompose this gas, retaining the carbon 
and setting free the oxygen. This process is known 
as the ^'fixation (sometimes assimilation) of carbon," 
and takes place chiefly in the leaves. The power to 
fix carbon is dependent in some way on the presence 
of the green coloring matter (chlorophyll), so that it 
is only those plants having green leaves that can use 
the carbonic acid. Such ]:)lants as mushrooms and 
other fungi, for instance, can not obtain their carbon 
in this manner but must procure it through the decom- 
position of organic matter, or in other words, must 
have their food jireviously prepared for them. Green 



l8 FIRST PRINCIPLES OF SOIL FERTILITY 

plants, on the other hand, can manufacture their own 
food from the inorganic materials of the soil and atmo- 
sphere. 

Sunlight Necessary to Carbon Fixation. — The de- 
composition of carbonic acid by the plant, and the 
assimilation of the carbon take place only during the 
daytime. A certain amount of energy is necessary to 
break apart the carbon and oxygen of carbonic acid, 
and this energy is furnished by the sunlight. The 
stronger the light the faster the fixation of carbon. 
This explains the commonly observed fact that most 
plants grow more vigorously in full sunlight than in 
shade or diffused light. The plant has not the power 
to use carbonic acid in the absence of light, so that this 
process ceases during the night. It is well known that 
seeds will germinate in the dark, and produce a feeble 
spindling growth of pale foliage, but that the plants 
so produced soon cease to develop. Such plants grow 
until they exhaust the food stored in the seed, but have 
no power to use the food in the air and soil, and 
analysis shows that the plant contains less dry matter 
than w^as present in the seed. In the presence of light, 
however, the plant absorbs the carbonic acid of the air 
by means of its leaves, and causes the carbon to com- 
bine with the water and mineral matter taken in 
through its roots to form carbohydrates, proteids and 
the other complex compounds of which the plant is 
composed. 

Carbonic Acid the Sole Source of Carbon. — It has 
been thoroughly demonstrated that the green plants 
derive their carbon solely from the carbonic acid of 
the atmosphere, and are not dependent in any way 



ATMOSPHERE AS A SOURCE OF PLANT FOOD 1 9 

Upon the carbonaceous matter in the soil. In fact, 
that they are incapable of using carbon except in the 
form of carbonic acid gas. The quantity of carbonic 
acid in the air seems so insignificant that it might be 
feared that the supply might some day be exhausted. 
The bulk of the atmosphere is so enormous, however, 
that the total amount of carbonic acid is very large. 
Johnson calculated that the atmosphere when taken to 
its entire height contains not less than 3,400,000,000,- 
000 tons of carbonic acid. This amounts to about 28 
tons over every acre of the earth's surface, and as only 
one-fourth of the earth's surface is land he estimated 
that the carbonic acid in the air is sufficient, without 
renewal, for a hundred years of growth. As a matter 
of fact, the supply of this gas is being constantly re- 
newed, and at such a rate that the proportion found in 
the air remains about constant. When w^ood or coal 
or any other substance containing carbon is burned, 
carbonic acid is formed and passes into the atmosphere. 
This gas is produced during all kinds of decay and 
fermentation. Animals live directly or indirectly on 
plants, and breathe out the carbon they consume in the 
form of carbonic acid gas. It will thus be seen that 
the carbon is continually in circulation, being combined 
by the plant into complex compounds only to be broken 
down, and returned again to the air through these 
various agencies. In all probability that now present 
in the air has been many times built up into organic 
matter, only to be again set free by decomposition. 

Numerous experiments have proved that the supply 
of carbon in the air is ample for the largest crops. To 
be sure, in certain pot experiments a larger yield was 



20 FIRST PRINCIPLES OF SOIL FERTILITY 

obtained by increasing the carbonic acid in the air, but 
under field conditions the yield is limited by other 
factors, and never by the supply of carbon. 

Carbon Costs the Farmer Nothing. — The point of 
practical importance brought out by this study of the 
fixation of carbon is that the carbon is furnished free 
of cost. In other words the carbon compounds pro- 
duced in the crop result in no impoverishment of the 
soil. Hence, there is no need of supplying strictly 
carbonaceous manure to the field, as the crop does not 
use the carbon in the soil. It will be shown later that 
such manures may be indirectly beneficial to the plant, 
however. 



CHAPTER III 

NITROGEN AS A PLANT FOOD 

Nitrogen the Most Costly Plant Food. — A refer- 
ence to the table given in Chapter I shows that only 
abont lYz per cent of the dry matter of the corn plant 
consists of nitrogen. Some plants contain more nitro- 
gen than this, but the amount rarely equals 3 per cent 
of the dry matter, or six-tenths of one per cent of the 
green plant. In spite of the small quantity of nitrogen 
in the crop it is the most important of all plant foods 
from the practical point of view. In fact the solution 
of the problem of the maintenance of fertility depends 
upon an economical method of conserving and renew- 
ing the nitrogen supply of the soil. This does not 
imply that nitrogen is more necessary to vegetation 
than are the other constituents, but that it is the most 
expensive element to be furnished by means of ferti- 
lizers, and is also, unfortunately, the element most 
easily lost and wasted. 

The Nitrogen of Most Plants Comes from the Soil. 
— Most of the crops raised by the farmer are entirely 
dependent upon the soil for their supply of nitrogen. 
The greater part of the nitrogen present in the soil is 
locked up in the insoluble organic matter, and in this 
form is not available to plants. Some of the nitrogen 
exists in simple compounds called nitrates, which con- 
sist of nitric acid combined with one of the mineral 
elements of the soil. The majority of farm crops can 

21 



22 FIRST PRINCIPLES OF SOIL FERTILITY 

use only that part of the nitrogen in the soil that is 
present as nitrates, so that so far as the nitrogen is 
concerned, the fertility of the land depends upon its 
nitrate content. The nitrate present in the soil at any 
one time is exceedingly small, but under proper con- 
ditions the supply may be renewed with sufficient 
rapidity to meet the needs of the plant. 

Source of the Nitrogen of the Soil. — A small part 
of the nitrogen in the soil is derived directly from the 
atmosphere. Minute traces of ammonia (a compound 
of nitrogen and hydrogen) are always found in air, 
and during electrical storms small quantities of the 
nitrogen and oxygen in the atmosphere are combined 
to form nitric acid. These substances are dissolved in 
the rain water during showers and are carried into 
the soil. The quantity received by the soil from this 
source is very small, amounting only to from 3 to 8 
pounds an acre a year, the maximum amount being less 
than one-tenth of that required by a crop of corn. 
Nearly all of the nitrogen in the soil is present in the 
more or less decayed organic matter left behind by the 
plants that it has previously produced. Plants build 
up the nitrogen into complex protein compounds, and, 
under ordinary conditions, when they die these sub- 
stances in connection with the other constituents of the 
plant become a part of the soil. As long as the nitrogen 
remains in this form it is of no value to the new genera- 
tion of plants, for the organic matter must first be 
decomposed, and the nitrogen changed into the form 
of nitrates. 

Nitrification. — The soil must not be regarded as an 
inert mass of mineral matter and refuse of former 



NITROGEN AS A PLANT FOOD 23 

plant growth. It is, in fact, an immense laboratory 
in which millions of tiny workmen are bringing about 
marvelous chemical changes. The principal factors 
concerned in these transformations are bacteria, of 
which, it is estimated, there are present in the neigh- 
borhood of one hundred fifty millions in each ounce of 
surface soil. Some of these bacteria cause the fer- 
mentations and decay that return the carbonic acid to 
the air. Others, and these are of particular interest 
here, bring about the decomposition of the nitrogenous 
organic matter with the ultimate production of nitrates. 
The transformation of organic nitrogen into nitrates 
undoubtedly results from the action of more than one 
species of bacteria, and takes place in three or more 
different steps. The organisms necessary to produce 
these changes are ordinarily present in all soils. Nitri- 
fication takes place only when the temperature is more 
than 5° above freezing, and becomes more rapid with 
rise of temperature. Hence, it ceases during the winter 
months, and is most vigorous during the hot months 
of midsummer. The nitrifying bacteria can not live 
without a sufiicient supply of oxygen, and, for this 
reason, stirring up the soil, and thus introducing air, 
increases the rate of nitrification. Nor can these bac- 
teria thrive in a soil that is acid, so that the presence 
of carbonate of lime, or some other substance that will 
neutralize any acid produced in the soil, is essential 
to nitrification. All of these points will be discussed 
in greater detail later; for the present it is sufficient 
to emphasize the importance of the process of nitrifi- 
cation to the growing crop. So vital indeed, is the 
subject that successful agriculture may be said to de- 



24 FIRST PRINCIPLES OF SOIL FERTILITY 

pend largely upon providing proper conditions for 
rapid nitrification. 

Denitrification. — While the nitrifying bacteria may 
be said to be the farmer's friends, there are, unfor- 
tnnately, in the soil other organisms which produce 
evil results. One class of these, known as denitrifying 
bacteria, decompose the nitrates, and perhaps some 
other nitrogenous compounds, with the final result that 
the nitrogen is set free and returned to the air in its 
elemental condition. This process of course, robs the 
soil of a part of its nitrogen, and is especially un- 
fortunate because it removes the part that was most 
readily available to the crop. The conditions that are 
detrimental to nitrification (/. c. lack of oxygen, pre- 
sence of acidity, etc.) are those that favor denitrifica- 
tion, so that the farmer in producing proper conditions 
for the former desirable process is at the same time 
preventing the injurious denitrification. 

Can Plants Use Free Nitrogen of the Air? — About 
four-fifths of the volume of the air consists of the ele- 
ment nitrogen, so that if this were generally available 
to plants there could be no such thing as ''nitrogen 
starvation." Perhaps no question in the realm of agri- 
cultural chemistry, or plant physiology, has received 
so much attention as the relation of the plant to the 
nitrogen of the atmosphere ; but many points still re- 
main to be investigated. The question heading this 
paragraph can best be answered by a very brief histor- 
ical review of the subject. At one time it was generally 
believed that the air was the sole source of the nitrogen 
supply for the plant. The first important experiments 
that indicated the contrary were those in which Bous- 



NITROGEN AS A PLANT FOOD 2$ 

singault grew plants in sterile soil free from nitrogen, 
the plants being so protected that they came in contact 
with no nitrogen save that of the air. The plants grew 
for a short time only, and upon analysis showed that 
they contained no more nitrogen than was present in 
the seed. Similar experiments conducted by Ville gave 
contrary results. To decide the matter, a great number 
of painstaking experiments were carried out at Roth- 
amsted, England, all of which confirmed the results 
obtained by Boussingault, and the question was con- 
sidered settled by most experimenters. About the same 
time field tests were conducted at Rothamsted which 
indicated that when clover and other leguminous plants 
were grown, there was an actual gain of nitrogen in 
the soil, in addition to that removed by the vegetation, 
while the growth of cereals resulted in a loss of nitro- 
gen. Other experimenters also arrived at the con- 
clusion that clover has the power of procuring nitrogen 
from some unknown source. Farmers had known for 
some time that wheat grown after. clover does as well 
as when manured with a nitrogenous fertilizer. Some 
writers tried to explain this fact by assuming that the 
clover roots bring up the nitrogen from the deep sub- 
soil and leave it near the surface, but the explanation 
was never satisfactory. 

The conditions under which the pot tests were con- 
ducted were not normal, as the plants were grown in 
prepared soils that had been heated to kill any bacteria 
they might contain. It occurred to Atwater that plants 
grown under natural conditions might use free nitrogen 
even though they did not under the conditions of these 
experiments. He, therefore, grew plants in pots in the 



26 FIRST PRINCIPLES OF SOIL FERTILITY 

Open, analyzing the soil before the experiment and the 
soil plus the plant at the end of the growing season, 
correcting for the nitrogen carried down in the rain 
water. He found that while in most cases there was 
no gain of nitrogen, in some cases there was a decided 
increase. Those plants which produced a gain in 
nitrogen invariably belong to the same family as the 
pea, bean, clover, etc., or in other words to the so- 
called "legumes" or "leguminous plants." It remained 
for Hellriegel to explain this phenomenon. He re- 
peated the experiments of Boussingault with this varia- 
tion that to the soil in some of the pots he added a 
small quantity of water leached from a natural soil 
so as to introduce any bacteria that might exist natural- 
ly in the earth. He found that in the perfectly sterile 
soil there was no gain in nitrogen by any of the plants, 
but that in the pots to which the soil leachings had 
been added the legumes grew vigorously, while the 
cereals produced only feeble and short-lived plants. 
Upon examination of those legumes which made 
marked growth he found that they all had numbers of 
small nodules or tubercles on their roots, and these 
nodules on inspection were found to contain innumera- 
ble bacteria. 

Further tests have demonstrated that when legu- 
minous plants are grown in soils contaiiiing the proper 
bacteria, they can indirectly make use of free nitrogen, 
and are practically independent of the nitrogen in the 
soil. This property is not a function of the legume 
itself, but of the bacteria that produce the nodules, 
and in the absence of these organisms the legumes are 
quite as dependent upon the supply of nitrates as are 



NITROGEN AS A PLANT FOOD 



27 



the other orders of plants. It may be further said 
that so long as the leguminous plant can procure in the 
form of the nitrates all the nitrogen it needs the nodules 




NO 

N 



NO N 
BAG 



Showing the power of clover to obtain nitrogen by means of the bacteria in the 
root-noduies. Both pots received all the elements of plant food except nitrogen 
The pot on the right was inoculated with the proper bacteria, while that on the 
left was not. 



will not be formed. For that reason, in a soil rich in 
nitrogen the root tubercles may not be found on the 
legumes, even when the proper bacteria are present. 
Yet for all practical purposes it may be taken for 
granted that clover, peas, beans, alfalfa and other 



28 



FIRST PRINCIPLES OF SOIL FERTILFIY 



legumes derive the bulk of their nitrogen from the air, 
and that in growing them the farmer is not decreasing 
the nitrogen content of the soil, but may actually be 
adding thereto. 

Inoculation of the Soil. — Experience has shown 
that all soils do not contain the bacteria necessary to 




Root tubercles on soy beans. The left inoculated and the other uninocula- 
ted Tubercles appear only when the proper bacteria are present in the soil 

the fixation of free nitrogen by legumes. They may 
be introduced into a field by sowing with the seed a 
small quantity of soil from a field in which the legume 
has been successfully grown. This has been done so 
often as to leave no doubt of its practicability. Late 
investigations have shown that the same species of 
bacteria w411 not do for all legumes ; so that a soil, 
for instance, may grow clover to perfection, when soy 
beans or alfalfa will not thrive on it at all. This fact 
explains many of the disappointments experienced by 
farmers in the trials of some of the more recently 




Effect of inoculation on yield. The plant on the left came from a plot 
where all the plants had nodules on roots; the other from a plot where prac- 
tically none of the plants had nodules. The yield was in the ratio of the 
size of the plants shown in the illustration. 

29 



30 FIRST PRINCirLES OF SOIL FERTILITY 

introduced leguminous crops. While inoculation of 
the soil is of undoubted use in some cases, there is 
danger of overestimating its value. It must not be 
regarded as a panacea for all the ills of the soil. In- 
oculating a soil simply introduces the nodule forming 
bacteria, and if the failure of the leguminous crop was 
due alone to absence of these bacteria the results will 
be beneficial. It will in no wise overcome failure due 
to bad seed, improper preparation of the ground, ad- 
verse weather conditions, acidity of the soil, etc., and 
the farmer should assure himself that the soil con- 
ditions are as favorable as possible before he attempts 
inoculation. 

Other Ways in which Nitrogen is Fixed. — Within 
the last few years a number of bacteria have been dis- 
covered in the soil which have the power, when culti- 
vated in the laboratory, of using free nitrogen, and 
which do not grow in connection with the higher plants. 
These bacteria are found in most soils, and may be an 
important factor in maintaining the supply of nitrogen 
in the soil. At the present time it is impossible to say 
whether the nitrogen added to the soil in this way is 
of any considerable moment. 



CHAPTER IV 

SOIL AS A SOURCE OF PLANT FOOD 

Mineral Constituents of the Plant.— There still 
remains to be considered the mineral matter found in 
the ash, or that material which remains when the 
organic part of the plant is destroyed by burning and 
which corresponds exactly to the ashes left in the stove 
after burning wood. The substances found in the ash 
are all derived from the soil. It has not always been 
thought that they were necessary to plant growth. The 
earlier writers on agriculture considered only the or- 
ganic matter of the soil and certain constituents of the 
atmosphere as of any importance to the plant. These 
writers thought the presence of mineral matter merely 
accidental, and due to the fact that the plant took it 
because it was dissolved in the necessary soil water, and 
had no way of rejecting, or removing it. Later writers, 
however, preeminent among whom was Liebig, proved 
that the ash ingredients are necessary to the plant. 
A very simple experiment was sufficient to show that 
at least some of the mineral matter was essential to 
plant growth. Seeds were planted in quartz-sand in 
pots, to one of which nitrogen compounds alone were 
supplied, and to the other, nitrogen and a small amount 
of plant ash. The plants in the pot which received 
the ash grew to maturity, while those in the other pot 
made only a feeble, short lived growth. 

31 



32 



FIRST PRINCIPLES OF SOIL FERTILITY 



Essential and Non-Essential Elements, — The ex- 
periment just described proves that there is something 
in the ash that is required by the plant, but does not 
show whether only a part or all of the ingredients are 




Experiment to show the essential elements of plant food. Numbers 4, 7, and 1 1 
received all the elements of plant food while one element was withheld in each 
of the other tests. 



essential. This question naturally interested a number 
of investigators, and soon a mass of evidence was at 
hand. In order to determine which elements are 
essential, plants were grown, either in specially pre- 
pared sand or by the ''water-culture m.ethod," in such 



SOIL AS A SOURCE OF PLANT FOOD 33 

a way that they were supphed with ah the elements 
occurring in plants, with the exception of the one ele- 
ment under investigation. If the plant grew to maturity 
the element which was missing was deemed non- 
essential. If, on the other hand, the plant failed to 
develop, that particular element was considered to be 
essential. 

The numerous experiments of this kind which have 
been carried on show that of the ash constituents 
potash, lime, phosphoric acid, magnesia, iron and sul- 
phuric acid are absolutely essential to plant growth. 
Toward soda, chlorine and silica plants seem to be in- 
different, as they can grow to maturity in the absence 
of these substances. For this reason it is generally 
conceded that only ten of the thirteen elements found 
in the plant are essential to growth, soda, chlorine and 
silica being thought non-essential. Accepting this view 
and referring again to the table on page ii it is seen 
that 1,000 pounds of corn plant contain only 9 pounds 
of essential mineral matter or about 0.9 per cent. At- 
tention is called to the fact that these experiments ex- 
tended over only one generation, and that it is possible 
that an attempt to grow the crop through successive 
generations in a soil devoid of soda, chlorine or silica 
might show different results. 

One Element can not be Substituted for Another. 
— The experiments mentioned above have shown, not 
only that certain chemical elements are necessary to 
plant growth, but also, that it is not possible to replace 
these essential elements even by others which are simi- 
lar in chemical properties. In the chemical laboratory, 
for example, it is found that soda and potash are very 



34 



FIRST PRINCIPLES OF SOIL FERTILITY 



much alike in their action, and one may be used in place 
of the other in many operations. It would be a good 
thing for agriculture if soda could be substituted for 
potash as a plant food, as compounds of sodium are 
very inexpensive compared with potash compounds. 




Spinach : a full ration soda; b full ration potash 
One element of plant food cannot take the place of another in promoting plant 
growth. The pile on the right shows spinach grown with complete fertilizer. 
The pile on the left received the same fertilizer with potash replaced by soda. 

This point has been thoroughly investigated, and it has 
been demonstrated that soda can not take the place of 
potash as a fertilizer. As a definite amount of each 
of these elements is required for a certain yield, and 
none of the elements can be replaced by another, it 
seems to follow that the crop produced will be limited 
by the quantity of the essential element present in least 
proportion, compared with the requirements of the 
crop. In other words, if a field of corn can obtain 



SOIL AS A SOURCE OF PLANT FOOD 



35 



potash sufficient for only half an average crop, no more 
than this can be produced no matter how much of the 
other forms of plant food is present. 

How the Mineral Matter Enters the Plant. — It 
seems evident that the mineral matter must be taken 
up in some way by the roots. All are familiar with 
the fact that the soil is not a solid mass but consists 
of small particles, or ''grains," with air spaces between, 
these spaces in the surface foot amounting to fully half 
the bulk of the soil. These 
grains vary in size ac- 
cording to the character 
of the soil, being very fine 
in clay, and comparative- 
ly coarse in sandy soils. 
The roots of the plant 
push down between these 
soil grains, branching 
more or less, and spread- 
ing throughout the soil. 
Surrounding the growing 
tip of the root are great 
numbers of fine root hairs 
that work their way in be- 
tween and around the 
small soil grains, adher- 
ing closely to them and 
covering an immense 
amount of surface. It is 
on these root hairs that 
the plant is dependent 
for the absorption of its 




Root- hairs on wheat when very ycung 
and four weeks later. All the water 
and food from the soil enter the plant 
through the root-hairs. Note how 
closely the root-hairs adhere to the 
soil particles. (After Sachs) 

water and mineral food. 



36 FIRST PRINCIPLES OF SOIL FERTILITY 

It was once thought that plants actually took 
in the very small solid particles of soil, and that the 
purpose of cultivation is to render the particles minute 
enough for the plant to absorb. It is now known that 
no food can enter the plant unless it is in solution. 
Each soil grain is surrounded by a film of water, and 
this water contains dissolved in it tiny quantities of the 
mineral ingredients of the soil, including nitrogen in 
the form of nitrates. The root hairs absorb the mois- 
ture as it is required by the plant, and with it such 
mineral matter as it needs. Both water and the dis- 
solved matter enter the plant by the process known as 
osmosis. Each element is absorbed independently of 
the others, and the plant can in a way refuse to absorb 
more of any one ingredient when it has all that is 
needed for its growth. This ''selective power" of the 
plant (if it may be so called) is shown by the fact that 
two different kinds of crops grown on the same soil 
may differ greatly in their composition. The ratio 
between the chemical elements found in them may be 
entirely different in the two crops and may be, in a 
great measure, independent of the ratio existing be- 
tween these elements in the soil water. 

Soil Solutions Very Dilute. — The amount of min- 
eral matter in the soil water is very minute. In the 
second chapter attention was called to the fact that 
at least 300 pounds of water must pass through the 
plant to produce one pound of dry matter. The fact 
that the soil water contains mere traces of plant food 
probably accounts, in some measure, for the immense 
quantity of water used by the plant, as it must absorb 
this water to obtain the food it requires. The plant is 



SOIL AS A SOURCE OF PLANT FOOD ^iJ 

not entirely dependent upon the mineral matter actually 
dissolved in the soil water for its supply of food. 
The roots have the power of secreting- an acid sub- 
stance that has a solvent action on that part of the soil 
which is insoluble in pure water. This is shown by the 
root tracings often seen on pieces of limestone in the 
soil. It may be shown by growing a plant in a small 
quantity of soil placed on a piece of marble. If the 
marble is examined after a time the outlines of the 
roots can be seen distinctly where the acid substance 
has cut into its surface. How great a factor in ob- 
taining food this property of the plant is can not be 
stated at present on account of our limited knowledge 
of the subject. 

Function of the Different Food Elements. — Now 
that the source of the different elements required by 
the plant has been briefly discussed, it is desirable to 
have explained the special function in the vital pro- 
cesses of the plant performed by each of these sub- 
stances. Unfortunately but little is known in regard 
to this subject, for up to the present time it has almost 
defied investigation. Carbon, oxygen and hydrogen 
are found in all the organic compounds of the plant 
and form about 98^^ per cent of the green corn crop. 
Nitrogen is a constituent of proteids and is necessary 
to their formation. Sulphur is found in some of the 
proteids but its special function is not known. Phos- 
phoric acid is supposed to be in some way connected 
with the transportation of the proteids from one part 
of the plant to another. Potash is thought to be neces- 
sary to the conversion of starch into sugar and, con- 
sequently, to its removal from the leaves to other parts 



38 FIRST PRINCIPLES OF SOIL FERTILITY 

of the plant. As starch itself is insoluble, it must be 
converted into sugar before it can be transported. 
Iron is necessary to the production of chlorophyll. A 
plant grown in a soil devoid of iron contains no chloro- 
phyll and, therefore, does not possess the power of 
fixing carbonic acid gas and manufacturing starch. 
Lime probably performs a number of functions, one 
of which is to neutralize the poisonous oxalic acid 
formed in the plant and render it harmless by produc- 
ing the insoluble calcium oxalate. Of the part played 
by the other elements practically nothing is known. 

Other Ways in Which Plant Food is Lost. — In the 
first chapter it was suggested that the decrease in 
fertility of a soil might be due to the fact that the crop 
removes from it something that is essential to plant 
growth, and the following paragraphs have been de- 
voted to determining what these essential elements 
are. Before proceeding to apply the knowledge thus 
gained, brief mention will be made of two or three 
ways in which plant food may be lost, other than by 
removal of the crop: 

First, by leaching of the soil, or removal of plant 
food in the drainage water. For practical purposes 
nitrogen may be said to be the only element lost in this 
way. As the nitrogen removed by leaching is all in the 
form of nitrates, any loss from this cause is extremely 
unfortunate. The soil has the power of fixing most 
of the mineral elements, so that only traces of them are 
lost in the drainage water. The fact that certain mine- 
ral fertilizers are fixed by the soil can be shown by a 
simple experiment. A tall cylinder is filled with soil 
and to it is added a quantity of water in which are dis- 



SOIL AS A SOURCE OF PLANT FOOD 



39 



solved compounds containing nitrate nitrogen, phos- 
phoric acid and potash. If the water that leaches 
through this soil is analyzed, it is found that the potash 




It is a dangerous practice to allow soils to remain bare and exposed to washing 
rains. Thousands of acres of good lands have been destroyed in this country in 
the manner shown in this illustration. 



and phosphoric acid have been removed by the soil, 
but that the nitrogen all remains in the leachings. 

Second, by surface washing. In hilly countries this 
may be a very important factor. As the soil is re- 
moved bodily from the surface of the field, it follows 
that the loss in this case falls on all the food elements. 
It affects nitrogen and phosphoric acid more than the 



40 FIRST PRINCIPLES OF SOIL FERTILITY 

Other ingredients. Most of the nitrogen is in the or- 
ganic matter which is near the surface, and, being 
Hghter than the rest of the soil, is more easily washed 
away. In most soils the first foot contains a larger 
proportion of phosphoric acid than the subsoil. 

Third, by denitrification. This has been referred 
to in a previous chapter and may be of great moment 
in a soil that is not properly managed. The conditions 
that are desirable in the soil are such as best prevent 
denitrification, so that the farmer who understands his 
business need not fear this source of loss. 

It is evident that in all these cases the heaviest loss 
falls on the nitrogen, the most expensive element to 
supply, and emphasizes a former statement, that the 
maintenance of fertility is largely a question of an 
adequate supply of nitrogen. 

A Small Part of the Plant Food is Derived from 
the Soil. — Attention is again called to the fact that the 
atmosphere is the original source of 98^ per cent of 
the materials found in the green plant ; the carbo- 
hydrates, fats and fiber being composed of elements 
supplied in the form of water and carbonic acid gas. 
These substances are furnished free of cost in humid 
climates, the supply being practically beyond control, 
and their use by the plant results in no impoverishment 
of the land. The subject of practical importance to 
the farmer is the supply of the other i^ per cent of the 
plant, consisting of nitrogen and the ash elements 
which are derived directly from the solid particles of 
the soil. It has been shown that seven of these ele- 
ments are essential to plant growth. Experience has 
proved that only three of these elements (/. <?. nitrogen, 



SOIL AS A SOURCE OF PLANT FOOD 



41 



phosphoric acid and potash) arc hkely to become ex- 
hausted, or, in other words, that nothing- is gained by 
adding to the soil any of the other elements of plant 
food. This is due to the fact that the plant uses nitro- 
gen, phosphoric acid and potash in rather larger quan- 




What immense quantities of plant food this liill must contain, but who can tell how 
much of it is available to plants? 



titles than the other elements, and that they exist in 
smaller quantities in the ground, and not because they 
are any more essential to vegetation. Occasionally soils 
are found that are actually deficient in lime, but in most 
cases lime is present in sufficient abundance for the 
growth of the plant. In this study of the effect of 
the removal of the crop upon the amount of plant food 
in the soil, then, it will simplify matters to confine 



42 



FIRST PRINCIPLES OF SOIL FERTILITY 



attention to the three substances nitrogen, phosphoric 
acid and potash, assuming that all other elements are 
present in the earth in abundance. 

Amount of Fertility Removed by Crops. — The 
different crops vary greatly in the amount of the three 
valuable fertilizing ingredients which they contain. The 
following table gives the amount of nitrogen, phos- 
phoric acid and potash in i,ooo pounds of some of the 
important crops, the different materials being selected 
to show something of the range of composition. 



'AMOUNT OF FERTILIZING INGREDIENTS IN CROPS 



1,000 POUNDS OF 



Corn fodder, with ears 
Corn, earsonly . . . . 

Timothy hay 

Wheat, grain 

Oats, grain 

Clover hay 

Tobacco 

Cabbage 

Potatoes 



11 


Pounds of 

Phosphoric 

Acid 




17.6 


5.4 


8.9 


14.1 


5.7 


4.7 


12.6 


5.3 


9.9 


20.2 


8.7 


5.5 


16.5 


6.9 


4.8 


21.2 


5.5 


18.7 


24.5 


6.6 


40.9 


2.4 


1.4 


5.8 


5.7 


1.2 


3.8 



Notice the great difference in the amount of fertiliz- 
ing materials removed in i,ooo pounds of the various 
crops as shown in the table, especially under nitrogen 
and potash. For the purpose of this discussion the 



SOIL AS A SOURCE OF PLANT FOOD 



43 



percentage of fertilizing ingredients in the crop is not 
of so much importance as the total amount removed 
by it from each acre of ground. The next table gives 
the amounts of nitrogen, phosphoric acid and potash 
removed from an acre by a few of the common crops. 
{Adapted from Van Slyke.) 

AMOUNT OF FERTILITY REMOVED FROM AN ACRE 



KIND OF CROP 



Corn, grain only 45 bus. 

Clover hay 2 tons 

Cabbage 15 

Barley 30 bus. 

Wheat 15 

Wheat 

Oats 45 

Tobacco 1600 lbs. 

Timothy hay IJ^ tons 



^ s^ 



^^ 



82 
100 
56 
31 
62 
45 






<^ 



135 
51 
13 
26 
37 

200 
45 



An interesting point brought out by the table is the 
great difference in the total amount of plant food re- 
moved from an acre by the various crops. It is readily 
seen that certain crops must exhaust the fertility of the 
soil more rapidly than others, and common experience 
shows that the plants which remove large quantities 
of the essential plant foods are those that most quickly 
render the land infertile. 



44 



FIRST PRINCIPLES OF SOIL FERTILITY 



Amount of Plant Food in the Soil. — The bearing 
of the above facts upon the question of the maintenance 
of fertihty can not be fully shown, unless the amount 
of plant food existing in the soil is determined. Large 
numbers of analyses of soils have been made and, as 
might be expected, these analyses show great varia- 
tions in the composition of the soils. The following 
table gives the amount of nitrogen, phosphoric acid 
and potash in the first foot of typical sandy loam, clay 
loam and clay soils. 

AMOUNT OF PLANT FOOD PER ACRE IN THE SURFACE FOOT 



KIND OF SOIL 



s^ 



^^ 



Sandy loam 
Clay loam . 
Clay .... 



3.736 

4,789 
3.250 



7,326 
4,935 
5,600 



44,827 
12,600 



The large amount of plant food present in the soil is 
surprising, in view of the fact that it is so hard to 
maintain a satisfactory yield of crops. Comparing the 
last two tables it is seen that the analysis of the clay 
loam soil shows the presence of sufficient nitrogen for 
"jy crops of wheat yielding 30 bushels to the acre; 
enough phosphoric acid for 246; and potash to supply 
1,724 such crops. The second and third foot contain 
nearly as much phosphoric acid and potash as the sur- 
face foot, so that so far as these two substances are 



SOIL AS A SOURCE OF PLANT FOOD 45 

concerned the supply seems almost inexhaustible. Al- 
though the chemical analyses of many of the soils upon 
which wheat has been grown show fully as large 
amounts of plant food as the clay loam under dis- 
cussion, experience has demonstrated that long before 
the smallest number of crops mentioned above {i. e. 




The physical condition of the soil is as important as its chemical composition. 
The lumpy soil contains as much plant food as the friable soil, but the plant 
roots cannot penetrate the hard lumps to obtain it. 



yy) have been produced the yield will have so de- 
creased as to be unprofitable. 

Chemical Analysis does not Shov^7 Available Plant 
Food. — The reason for the apparent inconsistency be- 
tween the analyses of soils and actual results in raising 
crops is found in the fact that the chemical analyses 
give the total amount of nitrogen, phosphoric acid 
and potash in the soil, but do not indicate what part 
of these foods is available to the plant. The greater 
proportion of these substances is locked up in insoluble 
compounds, in which form the plant is incapable of 
using them. Smaller quantities have been changed by 
the forces of nature into a condition in which they are 



46 



FIRST PRINCIPLES OF SOIL FERTILITY 



available to plants. While the amounts of these mate- 
rials removed by the crop seem insignificant when com- 
pared with the total plant food in the soil, they may be 
very large in comparison with the available part. The 
unavailable, or "potential," plant food is gradually 
being made available, but not Vv^ith sufficient rapidity 
to replace that removed from the field at harvest. It 
will thus be seen that the present fertility of the soiL 
depends not upon the potential plant food it contains, 




Diagram illustrating the formation of a soil on a limestone hill 



but upon that which is immediately available to the 
plant, and that the yield will be limited by the element 
of this available plant food present in least quantity. 
Continuous cropping of the soil with the removal of 
everything from the field results in the exhaustion of 
the plant food which has been rendered available during 
the past ages. It will be interesting to study the origin 
of the plant food, and the manner in which it became 
available to the plants. 



CHAPTER V 

ORIGIN OF THE SOIL 

The Primary Soils. — All soils are derived primarily 
from the igneous, or original rocks, of which the 
granites and trap are good examples. Geology teaches 
that the earth was once a molten mass, and that upon 




The glaciers were important factors in soil formation 



cooling it solidified into rocks, of which those men- 
tioned are types. These rocks must have contained all 
of the mineral or ash elements of plant food, as no 
other source of them is conceivable. This plant food, 
however, w^as present in insoluble compounds, and in 

47 



48 



FIRST PRINCIPLES OF SOIL FERTILITY 



this form was not available to plants. The conversioii 
of this potential plant food into availitble forms was 
brought about by a number of agencies. Fortunately 
these changes can be studied at first hand in the lava 
beds resulting from volcanic eruptions. These beds 
have been transformed in an incredibly short time from 



1 -•>..,,. '^l 


iliP 


H 

^^1 






%mn 



The freezing of the water in the rock crevices helps to break the rocks into 
small particles 

beds of solid rock into more or less fertile soils, by a 
series of changes much like those to be described. 

The Rocks Must be Pulverized. — Evidently the 
first step toward the conversion of the solid rock into 
soil must have been the act of pulverization. A num- 
ber of natural agencies have taken part in the grinding 
of the original rock into the small particles in which 
they are found in the ground. The rocks h'ave been 



OkTGlN OF THE SOIL 49 

disintegrated throMgh the influence of heat and cold, 
freezing and thawing, and by the action of air, water 
and ice. Such rocks as the granites, for example, can 
easily be seen to consist of several different minerals. 
These substances are differently affected by heat and 
cold, expanding and contracting at different rates, and 
for this reason the ef- 
fect of changes in tem- 
perature is to separate ' p^ ^ 
the rock into its com- ' /^ 
ponent parts. All rocks '■ ^ ^i /^ ^. • -^ 
are more or less porous, ^ .^^ ^ "-^r 




and consequently, ab- '^^ m^ 

sorb water, and the ex- 
pansion of this water 
when frozen tends to ^ 

break the mass into "^' . jJ^ 

fragments. Perhaps 

«^^^^ :.-,, ^ ^ ^ • ^u- Microphotograph of a section of granite 

more important m this magnified 30 diameters. (By courtesy 

grinding process than Geological Department, Columbia Uni- 

either of these factors 

is the action of running water and moving ice 
in the form of glaciers. There is no need to discuss 
these forces in detail, for it will be sufficient for the 
present purpose if it be kept in mind that all of these 
influences combine to disintegrate and grind the sur- 
face rocks into smaller and smaller fragments, until 
they are reduced to the finest particles found in what 
is called the soil. 

Plant Food Must Be Made Soluble.— A soil pro- 
duced by mere ]nilverization of the rocks would not 
furnish proper food for the higher plants, as one can 



50 



FIRST PRINCIPLES OF SOIL FERTILITY 



readily imagine if he thinks how unsuitable pulverized 
granite would be for plant production. The essential 
elements locked up in these insoluble compounds must 
be transformed into materials that the plant can assimi- 
late, and water is an important factor in bringing about 
these chemical changes. Pure water has very little 





1 



Running water is constantly changing the face of the earth, cutting out 
ravines and grinding the rock to powder 



solvent effect upon the minerals of which the igneous 
rocks are composed. The water that enters the ground 
has dissolved in it small amounts of carbonic acid gas 
derived from the air, and water containing this gas 
will dissolve these minerals in appreciable quantities. 

A Fertile Soil must contain Nitrogen. — All the 
processes enumerated unite in transforming the mineral 



ORIGIN OF THE SOIL 



51 



matter of the rocks into forms available to plants, but 
the mineral foods alone can not support the higher 
plant life. It has been shown that to grow crops the 
soil must contain available nitrogen, and this must have 
been derived originally from the air. In a previous 
chapter it -was mentioned that small quantities of com- 
bined nitrogen are carried into the ground by the rain- 
water, and this amount, though very small, is probably 
sufficient to cnal)le plant growth to begin. Some bac- 





w «.'"■» v-WWJ ,. 



Effect of freezing on a piece of 
limestone 



Mosses growing on granite boulder. 
They must have small food require- 
ments or great powers of obtain- 
ing it. 



teriologists believe that the species of bacteria which 
can live upon mineral food alone, deriving all their 
nitrogen supply from the air, are important factors in 
the early nitrogen supply of the soil. 

First Plants very Simple Organisms. — \"egetation 
begins with the very simplest forms of plants such as 
the lichens and mosses, and is, of course, very scanty 
at first. These plants on dying become a part of the 
soil, all of the plant nutrients used by them being thus 
returned. Food that has once been used by plants is 
very readily . made available to succeeding crops, 
through the processes of decay and nitrification which 



52 



FIRST PRINCIPLES OF SOIL FERTILITY 



have been described. The soil is now able to produce 
a larger crop, as it contains the plant food in the pre- 
vious growth in addition to that added through the 
agencies detailed above. In this way the growth grad- 
ually becomes more abundant. The plants upon de- 
caying give rise to humus, and this increases the 




Effect of weathering on a limestone ledge. Notice that some plant or other 
takes advantage of every little accumulation of soil 



fertility of the land, both by being a source of plant 
food, and by increasing the water-retaining power. 
It will be shown later that humus is a very important 
factor in fertility. During the decompositions of the 
plants, which give rise to humus, acid substances are 
formed which act upon the rocks in such a way as to 
make more of the plant food available. One of the 
products of decay or fermentation is carbonic acid gas, 
which is dissolved in the soil water, and this gas-con- 



ORIGIN OF THE SOIL 53 

taining water is an important help in disintegrating 
the rocks. 

Root Bearing Plants Important in Soil Formation. 

— As the nutritive materials increase from these various 
causes, the lower and simpler forms of plant life are 
gradually replaced by those which are more highly 




The roots of plants are important factors in the pulverization of the rocks and 
the formation of the soil 

organized. With the advent of plants bearing roots, 
other factors in the formation of soils are introduced. 
The roots secrete an acid substance that has a solvent 
effect on the mineral matter of the soil, and assist 
mechanically in breaking down the rocks. All are 
familiar with the tremendous force exerted by plants 
in breaking apart rocks and stone, if once their tender 
rootlets obtain a foothold in a crevice. The roots 



54 



FIRST PRINCIPLES OF SOIL FERTILITY 



penetrate the soil sometimes to great depths, and, as 
they decay after the death of the plant, they leave in 
the soil little channels which serve to carry down water 
laden with carbonic acid, as well as to introduce the 
oxygen of the air, which in its turn, is a factor in bring- 




Fungi growing on an old stump. 
They hasten its decay and the re- 
turn of the plant food to the soil. 




Lichens growing on rock. They are 
among the early agencies con- 
cerned in soil formation. 



ing about chemical changes in the soil which assist in 
making plant food available. 

Legumes Increase Nitrogen of the Soil. — Sooner 
or later in the process of soil formation are introduced 
plants of the pulse family (leguminous plants) such 
as clover, vetches, lupines, etc., which can, through the 
agency of the nodule-forming bacteria in the soil, de- 
rive part of their food from the free nitrogen of the 
atmosphere. This peculiar property of leguminous 
plants is of paramount importance, for it is undoubtedly 



ORIGIN OF THE SOIL 



55 



Nature's principal method of increasing the supply of 
nitrogenous food in the ground. The nitrogen com- 
pounds accumulated by these plants eventually become 
a part of the soil through their decay, thus adding to 
its fertility. 

Soil Results from Combined Action of Various 
Agencies. — It will be readily understood that the vari- 
ous agencies .concerned in the formation of the soil do 
not act separately nor necessarily in any such order as 




STREAM 



Diagram showing the movement of the soil from higher to lower levels 

that in which they have been discussed. As a matter 
of fact, all the processes described take place simulta- 
neously. The lower plants do not wait for the rocks 
to be pulverized, for we see such organisms as the 
lichens growing on rocks from which it would seem 
impossible for them to obtain food. If the lichen is 
removed, grooves or furrows will be found en the 
surface of the stone, due to the action of the plant. 
Nor are all soils formed directly from the original or 
igneous rocks, for one of the effects of weathering, etc., 
is to separate such rocks as the granites into simpler 
substances, with the result, for example, that huge de- 



56 FIRST PRINCIPLES OF SOIL FERTILITY 

posits of limestone are formed in one place, and in 
another whole hills of sandstone. 

Movement of Soils. — The soil is almost constantly 
moving, for some of the same agencies which form 
soils are continually carrying them away. Running 
water grinds the rocks, but at the same time transports 




Lakes, ponds and swamps are gradually being filled by the movement of the 
soil from higher to lower levels 

the fine particles to lower levels. It cuts deep valleys 
in the surface of the earth and carries away the debris, 
depositing it at various distances from its source. 
Notice a stream muddied by a recent rain, the mud will 
be deposited somewhere to help form a soil. The soil 
is always moving from a higher to a lower level, con- 
sequently, it is thinnest at the top of a hill and deeper 
in the valley. Lakes and ponds are gradually filling 
up, and in time become fertile fields. If the pond is 
largely filled by the remains of the plants which have 
grown on it, a humus or peaty soil is formed. 



ORIGIN OF THE SOIL 



57 



Sedentary and Transported Soils. — Soils which 
have been formed from the rocks directly beneath them 
are known as ''soils in place" or sedentary soils. These 
partake very nearly of the composition of the under- 
lying rocks. Transported soils, on the other hand, 
may bear little resemblance in composition to the rock 
upon which they lie. Those deposited from water are 








Drift soils are distinguished by the presence of rounded boulders. They 
are usually fertile though variable in composition 

called "alluvial soils" and are found in the river valleys 
and in the beds of former lakes, and are usually very 
high in fertility. Those transported by glaciers are 
known as "drift soils." A large part of Northern 
United States is covered by drift which was pushed 
down from the north by the glaciers that once covered 
that section, and was left behind as the ice melted 
away. Drift soils are distinguished from all others by 
the presence of rounded boulders of various sizes, and 
are usually fertile, although very variable in composi- 
tion. 



58 



FIRST PRINCIPLES OF SOIL FERTILITY 



Nature's Methods Contrasted with Man's. — The 
important lesson to be learned from a study of the 
origin of the soil is, that Nature undisturbed has many 
ways of adding to the supply of available plant food 
in the soil. The various forces that have been under 
discussion have all tended to change more and more 
the potential food into forms that can be assimilated 




Nature undibLuroed returns all the plant food removed from the soil, by the 
decay of the plants which it has produced 



by the plants, so that the amount of vegetation which 
the soil can produce has been constantly increasing. 
Under natural conditions this growth is not removed 
from the ground, but is again made available, so that 
the land is constantly increasing in fertility. Thus it 
will be seen that the fertility of the virgin soils is the 
result of accumulations due to a variety of forces act- 
ing doubtless through countless ages, a period during 
which practically nothing has been removed from the 
soil while much has been added thereto. 



ORIGIN OF THE SOIL 



59 



Man, on the contrary, has reversed this process and 
while adding Httle to the soil has removed much there- 
from. Through the constant harvesting of crops and 
leaving the ground bare and exposed to the action of 
the elements, he is rapidly depleting Nature's store of 
food, and the yield steadily becomes smaller. The 
effect upon the physical condition of the soil due to the 



fwf"^ 


W^"'' 




1 "^4 


A^m 






\w i 




^S'^si^J 


(Oi,.---^ 






• . ■ ■ y 


'■ '* ', 










m 




■ N-l 


I \ 






- % . 




''M 


**''~«fe-„ \y 






; ■■ V" ?*'■' 






X. \ 




1 - 


i J^ 


1 ^ 


^^•f^ff^t^f^w^ ' 




^^^^r^^^H 


^^otI 


^^ ->^.. 


.''".,' 


■1 


Wf -^ *• '-- *-*,™*^ 'nT.w 




I^^^Sml^^' '" -;»<*?' 


fi 


i^<, X 


1' ^ 


m^M 


*|^^5^' ' ■' '■ 


' ,r^-^*^ 


-■'/_:"• 


1^ ...... - 


a^^^WP 


^t.-&d:' 


.;\ : ■" ■■'"■ 




^«i.J«»**- «^- _. ^^, 


•T 2l 


i^9^:ZSl 


»^a0^«^ime^~'> 




fimmmm^ •%*«*- 


3 


r Jri'**'*'^*?' 


^W^^^A-^ 




^^^7^ mmf^ 




.<«f^..«:.,«^~ 


'^^^^T^imStKKl 



Who can tell how long it has taken this stream to cut this deep gorge 
the limestone 



removal of all vegetation is serious, for in this way the 
soil is deprived of its humus-making materials, which 
is unquestionably quite as important as the actual loss 
of the chemical elements of fertility. 

How to Prevent Exhaustion of the Soil.~Although 
Nature's method of maintaining the fertility of the soil 
is without doubt the most effective, it is of course im- 



60 FIRST PRINCIPLES OF SOIL FERTILITY 

practicable for the farmer, for he must remove most 
of his crops from the field in order that they may be 
put to the various uses for which they are raised. A 
study of the formation of the soil, however, suggests 
two things that he can do to prevent the exhaustion of 
the fertility. The first is so to treat the soil as to assist 
and hasten Nature in the process of converting poten- 
tial plant food into available forms ; and to guard 
against a too complete destruction of the organic matter 
in the soil. The second is to return to the soil an 
amount of nitrogen, phosphoric acid and potash equi- 
valent to that removed by the crop. 



PART II 

MAKING POTENTIAL PLANT FOOD 
AVAILABLE 




^ Q. 
o 



if 



o -O 

W o 
§^ 



CHAPTER VI 



TILLAGE 



Tillage Increases Feeding Ground for Roots. — 

The most efficient means of assisting nattire in the con- 
version of unavailable food into forms that the plant 



( "^ ■- 


^ ^.J^j^L ^. M;^ ^ 


■H^Jltfl 




|||iyiiiiiiiiiiinMiiiiiiiiifimniii<iiii||i,<,<<,.<,^,<,,^^ 


H|---__--- 


lii^Ai^ 


f 


^ 


^^m 


k ■■ . 


; . ' -' ^\ jp>.. 



Plowing is the most important t'llage operation. It should be so done as to 
leave the minimum amount of work for the harrow, etc. 

can use is good tillage of the soil. Tillage, in the sense 
in which it is used here, signifies any operation of 
stirring and pulverizing the soil by means of plows, 
harrows, cultivators or any other implement, either 
before or after the seed is sown. 

The most noticeable result of tillage is that the soil 
is made finer, the large lumps being broken up into 
smaller particles, and in this way Nature's work in the 

63 



64 FIRST PRINCIPLES OF SOIL FERTILITY 

formation of soils is accelerated. Pulverization of the 
earth is beneficial in many ways. In the first place, 
loosening the soil makes it easier for the plant roots 
and root-hairs to penetrate it. Mention has been made 
of the fact that all soils are composed of grains of 
greater or less dimensions separated by air spaces. The 
tender root-hairs must push their way in between these 
soil-grains, as it is impossible for them to penetrate 
the solid particles themselves. It must be evident that 
the more the soil is pulverized the larger the number 
of the openings between grains, and, consequently, the 
greater room for root growth. 

The plant is dependent upon the root-hairs for its 
supply of mineral food and, as these hairs grow only 
between and around the soil grains, it is apparent that 
they can feed only on the surfaces of these particles. 
Good tillage increases the amount of surface exposed 
to the roots by breaking the large lumps into small 
grains ; and the more complete the pulverization the 
larger the area from which the plant can obtain its 
food. The rapid increase of surface due to breaking 
down the lumps of a soil in poor tilth seems almost 
unbelievable to one who has given the subject no 
thought. An example will serve to illustrate what is 
meant: A cube, 2 inches on the side, presents a sur- 
face of 24 square inches. If this cube is cut once in 
each direction 8 cubes are formed, each one inch on a 
side, giving a total of 48 square inches of surface, so 
that cutting only once in each direction doubles the 
amount of surface. Thus, theoretically, a plant should 
be able to derive twice as much food from the eight 
small cubes as from the large one. 



TILLAGE 6c 

Tillage Hastens Chemical Changes in the Soil.— 

Stirring- the soil is of great advantage in bringing to- 
gether particles which have not before come into con- 
tact. In this way chemical changes may take place 
that render potential plant food available, for sub- 
stances having different chemical properties are tiiiis 




An incompleted soil. Good tillage will hasten the decomposition of the rocks 

enabled to act upon each other. The changes whereby 
potash and phosphoric acid become "fixed" in the soil 
are reactions of this class. The changes brought about 
by freezing and thawing may also be accelerated by 
proper tillage. This is made use of by some farmers 
who plow heavy, lumpy land in the fall so that it may 
be exposed to the influence of the weather during the 
winter. For this purpose the land is so plowed as to 
leave it rough and with the largest possible area ex- 
posed to the weather. Freezing and thawing bring 
about disintegration of the clods in much the manner 
mentioned in the chapter on formation of the soil, and 
the resulting improvement is most remarkable in some 
classes of soils. 



66 FIRST PRINCIPLES OF SOIL FERTILITY 

Tillage Aerates the Soil. — One of the most ad- 
vantageous results to be obtained from tillage is the 
aeration of the soil. The introduction of the oxygen 
of the air into the soil is of benefit in a number of ways. 
In the first place, a certain amount of air in the soil is 
necessary for the growth of all plants usually raised 
on a farm. The roots can not live without air any 
more than those parts which grow above ground. That 
air is needed by the roots can easily be shown by plac- 
ing a pot containing any ordinary plant in a jar of 
water so that the soil will always be saturated. In 
a short time the bad effects will be noticeable on the 
plant. The plant does not decline because the water 
is injurious but because the presence of the water ex- 
cludes the air from the roots. Oxygen is also neces- 
sary to the germination of seeds, for it is a well estab- 
lished fact that seeds will not germinate in the absence 
of oxygen. 

The oxygen of the air has a direct chemical action 
upon the mineral matter of the soil in that it tends to 
make the latter soluble. It also prevents the formation 
of certain compounds (notably the sulphides of iron) 
which are injurious to vegetation. 

Tillage Aids Nitrification and Prevents Denitri- 
fication. — All fertile soils contain a considerable 
amount of organic matter, and the presence of oxygen 
is necessary to its decomposition. Attention has been 
called to the fact that the soil contains innumerable 
bacteria, a part, at least, of which are concerned in the 
decay of organic matter, and those which are beneficial 
to the farmer can not live without oxygen. One class of 
these bacteria decomposes a part of the organic matter 



TILLAGE 67 

with the formation of carbonic acid gas, and it has 
been shown that this gas dissolved in the soil-water 
is a great factor in making plant food soluble. As 
this decomposition goes on more rapidly in well aerated 
soils it will be seen that this is one reason for the in- 
creased fertility due to thorough tillage. The nitri- 
fying bacteria previously mentioned thrive only in the 
presence of a sufficient supply of oxygen. Most of the 
nitrogen of the soil is locked up in insoluble organic 
compounds, and before it can be used by plants it must 
be converted into the form of nitrates. This process 
takes place only in a soil well supplied with oxygen, 
and experience has proven that this process is very 
materially hastened by frequent cultivation. The ex- 
treme importance of this process of nitrification has 
already been commented upon, and it remains only to 
say that tillage w^ould pay for itself if it did no more 
than hasten nitrification. 

Thorough aeration of the soil prevents the action 
of the denitrifying bacteria, as these bacteria thrive 
best in a soil devoid of oxygen. Acidity of the soil is 
also favorable to the grow^th of the denitrifying bac- 
teria, and as the presence of sufficient oxygen in the 
soil tends to keep it sweet it is thus helpful in pre- 
venting denitrification. 

The bacteria which enable leguminous plants to use 
free nitrogen are also dependent upon the air in the 
soil, for not only do they need oxygen, but experiments 
have shown that it is only from the air in the soil that 
they can draw their supply of nitrogen. It. is neces- 
sary, therefore, in order that leguminous plants may 
profit by the nodule-forming bacteria, to have the soil 



68 FIRST PRINCIPLES OF SOIL FERTILITY 

in such condition of tilth that the air may freely cir- 
culate through it. 

Tillage Increases Amount of Available Water. — 

Tillage not only increases the amount of surface on 
which the plants can feed, but at the same time en- 
larges the water supply by giving the soil greater 
capacity for holding moisture. Attention has been 
called to the fact that each soil-grain is surrounded by 
a film of water which is called the capillary water or 
film moisture. The plant is dependent upon this film 
moisture for its supply, and it is readily seen that the 
amount of capillary water that the soil can retain de- 
pends upon the aggregate surface area presented by the 
particles of which it is composed. The rate at which 
this area, and the consequent amount of available mois- 
ture increase, is strikingly brought out by King in his 
book entitled 'The Soil" from which the following is 
quoted: ''Suppose we take a marble exactly one inch 
in diameter. It will just slip inside a cube one inch on 
a side, and will hold a film of water 3.1416 square 
inches in area. But reduce the diameters of the mar- 
bles to one-tenth of an inch, and at least 1,000 of them 
will be required to fill the cubic inch, and their aggre- 
gate surface will be 31.416 square inches. If, however, 
the diameters of these spheres be reduced to one- 
hundredth of an inch 1,000,000 of them will be required 
to make a cubic inch and their total surface area will 
be 314.16 square inches. Suppose, again, the soil par- 
ticles to have a diameter of one-thousandth of an inch. 
It will then require 1,000,000,000 of them to fill com- 
pletely the cubic inch, while their aggregate surface 
must measure 3141.59 square inches." Another way of 



TILLAGE 69 



Stating the same fact is that if an acre of ground is so 
tilled as to reduce the average diameter of the soil 
particles to one-tenth the original diameter, the plant 
now has ten acres from which to draw its supply of 
water and mineral food for each acre it had before; 




The old-fashioned home-made planker is sometimes very useful for pul- 
verizing the soil 

and the soil is enabled to hold as film moisture ten 
times as much water as it could in the first instance. 

Tillage to Conserve Moisture. — From what has 
been said regarding the importance of water to the 
plant it must be apparent that one of the chief problems 
of agriculture is to maintain a proper degree of mois- 
ture in the soil. It seldom happens that a crop can ob- 
tain from the soil the amount of water necessary for 
a maximum yield, and great skill is required to keep 
it from suffering for lack of moisture during the hot 
summer period of scanty rainfall. While man can do 
nothing in the way of distributing the rainfall through- 



70 FIRST PRINCIPLES OF SOIL FERTILITY 

out the growing season, he can, by a judicious use of 
tillage methods, do much toward saving the excess of 
moisture precipitated in the early spring, for the use 
of the plant during the drier weather of the summer. 
One way in which tillage accomplishes this end is by 
increasing the capacity of the soil for storing water, 
as described in the preceding paragraph. It must also 
be evident that the loosening of the ground incident 
to tillage makes it easier for the rain to enter the soil, 
and tends to prevent loss by surface washing, as the 
water sinks into the soil instead of running away. 
Special mention might be made here of the "earth 
mulch" and late fall, and early spring plowing, as 
methods of tillage especially recommended for the con- 
servation of soil moisture. 

The Earth Mulch to Conserve Moisture. — During 
dry weather water is constantly being evaporated from 
the surface of the ground. Under ordinary conditions, 
where the soil is somewhat firm, water is drawn up 
from below by capillary attraction to replace that re- 
moved by evaporation. As this may be very rapid in 
the hot dry weather of midsummer the result is that 
the water is virtually pumped out of the soil until it is 
too dry for good plant growth. If something is done 
to break this capillarity the water can not be brought 
up from below. This is the end accomplished by the 
earth mulch, which is simply a layer two or three inches 
deep of very dry soil, so dry and loose that it can not 
take up the water from the layer next beneath it. The 
same end can be attained by covering the ground with 
loose straw or other similar material, the principle 
underlying both kinds of treatment being the same. 



TILLAGE 71 

To make an effective earth mulch the cultivation should 
be shallow and frequent, the aim being to make the 
layer as dry as possible. A rain, of course, will again 
compact the loose earth, and renew the capillarity, so 
that the cultivation should be repeated as soon as may 
be after a rain. Even in the absence of rain the mulch 
will sooner or later become compact of itself if left too 




Soil which is badly in need of tillage. The cracks allow large amounts of 
water to be lost by evaporation 

long without stirring. It is desirable to loosen the soil 
more frequently in the spring than is necessary later 
in the season. A mulch about three inches deep has 
been found to be most effective in conserving moisture, 
and it has also been shown that mulches produce re- 
latively better results in sandy soils than in clay or 
loam. 

Late Fall Plowing to Conserve Moisture. — Plow- 
ing the ground late in the fall tends to save the mois- 
ture, as the loose ground turned up by the plow pre- 
vents loss of water by evaporation. The broken uneven 



72 



FIRST PRINCIPLES OF SOIL FERTILITY 



surface also makes it possible for the soil to absorb 
more of the water from the winter rain and snow. An 
experiment reported from Wisconsin shows that a plot 
plowed in the fall contained 1.15 acre inches more water 
than an adjacent plot not so plowed. It must be borne 
in mind, however, that fall plowing is not a practice 




The tube roller crushes the clods without compacting the soil so much as 
the solid roller 



capable of universal application, for there are certain 
hard soils with a low humus content which may be 
badly puddled if fall plowed. Here, as everywhere in 
farming, good judgment is called for on the part of the 
farmer. 

Early Spring Plowing to Conserve Moisture. — 
Plowing the ground very early in the spring is a 
rational practice, for there is no other season when 
tillage is so effective in conserving the moisture of the 
soil. King reports one experiment where early plowed 
ground, seven days after plowing, contained an amount 



TILLAGE 73 

of water equal to 1.75 inches in excess of an adjoining 
plot which was not plowed. Quiroga, in a thesis pre- 
sented to the College of Agriculture, Ohio State Uni- 
versity, reports that the moisture content of the early 
plowed plots was higher than the late plowed through- 
out the season. He found also that the available nitro- 




Weeds are objectionable because they remove large quantities of water and 
available plant food which are needed by the crop 

gen was much higher, in the early plowed plots, and 
that the yield of corn was greater. All evidence in- 
dicates that the soil should be stirred as early in the 
spring as can be done without injury to its texture, 
either by plowing or by the use of some form of culti- 
vator or harrow. 

Tillage Destroys Weeds.— Lastly, tillage is useful 
in destroying weeds. Weeds should not be permitted 
to grow because they rob the crop of its moisture and 
plant food. During growth all plants pump up water 
by means of their roots, and give it ofif through the 
leaves. It has been shown that at the best the supply 



74 FIRST PRINCIPLES OF SOIL FERTILITY 

of water in the ground is seldom sufficient for a maxi- 
mum crop so that any withdrawal of water from the 
soil by the weeds works a positive injury to the de- 
sirable plants. While it is probable that the weeds do 
the greatest injury to the crop by depriving it of water, 
they also rob it of nitrogen and mineral food. Some 
farmers argue that if the weeds remain on the ground 
they are removing no fertility, but it must be remem- 
bered that they are using that portion of the plant food 
that could be used by the crop and that the weeds must 
decay before this food is again rendered available, so 
that so far as the present crop is concerned the food is 
as completely removed as it would be if taken from the 
field. , The destruction of weeds was formerly re- 
garded as the only reason for tillage after seeding. 
It is now known that stirring the soil has a distinct 
value in itself, and that the killing of the weeds is 
really secondary. In fact if the farmer so tills his 
farm as to reap the maximum benefits to be derived 
from this process he will have no need to worry about 
the weeds. 



CHAPTER VII 

DRAINAGE AND IRRIGATION 

Film Moisture and Ground Water. — An important 
method for increasing the fertiHty of some classes of 
soils is that of underdraining by the use of tile or 





A wet soil is a cold so. I. Dry, well drained soils become warm earlier in the 
spring than those which are wet 



other means. Water exists in the soil in two principal 
forms, viz : as the film or capillary moisture previously 
discussed, and in the form known indiscriminately as 
free water, ground water, or hydrostatic water. In the 
latter condition the water occupies the spaces between 
the soil grains, and is not held by the attraction of 

75 



76 FIRST PRINCIPLES OF SOIL FERTILITY 

these particles. The surface level of this free water 
is known as the "water-table," and is situated in some 
soils very near the surface while in others it is many 
feet below. The exact height of the water-table can 
be readily ascertained by sinking a hole to such a depth 
that water will stand in it, the level of the water in the 
hole being practically that of the water-table. It is 
this free or ground water that supplies shallow wells 
and the ordinary springs. In some cases the water- 
table may be at the level of the ground or above it, 
as is obviously the case where marshes and lakes exist. 

High Water-Table Objectionable. — When the level 
of the free water is near the surface of the ground, the 
soil will be greatly benefited by some system of under- 
drainage, as this hydrostatic water is, for several rea- 
sons, injurious to the crop. Ground water limits the 
feeding space available to the plant, and, consequently, 
the amount of food it can obtain. Those plants that 
are of importance to agriculture must have their roots 
supplied with air, and investigations have shown that 
such plants do not send their roots below the water- 
table, because the spaces between the soil particles 
below this level are filled with water, thus preventing 
the entrance of air. In other words, the depth to which 
the plant will send its roots is determined by the posi- 
tion of the water-table. 

Free water makes the soil cold. A great deal more 
heat is necessary to warm water a certain number of 
degrees, than is required to raise the temperature of 
an equal weight of the dry matter of the soil to the 
same amount. A soil, therefore, that contains much 
water is harder to heat than one that is comnarativelv 



DRAINAGE AND IRRIGATION ^J 

dry. A very wet soil causes plant-food to become 
locked up in unavailable forms, and in some cases 
compounds are produced which are actually poisonous 
to the desirable plants. Km excessive amount of water 
in the soil also dilutes the plant-food in solution and 
makes it more difficult for the plant to procure sufficient 
nourishment. 

One of the most important considerations in this 
connection is the fact that the presence of free water 




!^ # 




A place that calls for underdraining. Such spots are a menace to the health 
as well as being unprofitable 

in the soil prevents nitrification and promotes denitri- 
fication. In water-logged soil nitrates are rapidly de- 
composed, the nitrogen being given off to the air in the 
free, or elemental condition ; and for this reason not 
only is the nitrogenous food in the soil destroyed, but 
the application of nitrogen fertilizers to such a soil 
results in great waste of this valuable element of 
fertility. 

Drainage Aerates and Warms the Soil. — Under- 
draining the field results in lowering the water-table 



78 FIRST PRINCIPLES OF SOIL FERTILITY 

to the level of the drain, the water flowing off through 
the tile instead of standing near the surface as stagnant 
water. A few ways in which this is of benefit to the 
soil may be indicated. The removal of the free water 
from the soil above the drain allows the entrance of 
air, and for that reason increases the depth to which 
the roots will penetrate. The entrance of air with its 
oxygen and carbonic acid, and the consequent greater 
depth reached by the roots and earthworms, are factors 
of importance in improving the texture of the soil. The 

SURFACE OF GROUND 



SURFACE OF GROUND WATER ^ ^,.,.. 



Ic/TILE 



/ \ /' "-^ ^xi ^*riLE 



Diagram showing the level of the ground water in a tile-drained field a few hours 
after a heavy rain 

rains will now soak down through the soil rather than 
run off the surface, and in this way the nitrogen in the 
rainwater is added to the soil, and surface washing is 
to a certain extent prevented. Rain in the spring is 
warmer than the ground, and as it percolates through 
the soil has a beneficial effect in warming it, thus put- 
ting it in condition to promote plant growth much 
earlier in the season. Evaporation of water from the 
surface of the soil tends to keep it cool, and as the 
amount of water near the surface is decreased by 
drainage, evaporation is also lessened. Well drained 
lands, therefore, maintain a higher temperature 
throughout the season than do those containing much 
free water. Drainage lengthens the season of plant 



DRAINAGE AND IRRIGATION 



79 



growth and promotes nitrification and other processes 
by which the plant food is made available. 

Drainage increases Available Water and prevents 
Injury from Drouth.— Paradoxical as it may seem, 
underdraining increases the amount of water available 
to the plant. The crop depends almost entirely on the 
capillary or film moisture for its supply of water, and 




In cold, undrained lands, where the water-table in the spring is high, the 
plants are shallow rooted, and when the drouth of summer lowers the 
water-table they suffer for lack of moisture. 

as has been said, the roots do not enter that part of the 
soil containing free water. Lowering the water-table 
greatly increases the total amount of film moisture, as 
all that part of the soil from which the free water has 
been removed is capable of holding capillary water. 
Thus it will be seen that while the total amount of 
water in the soil is decreased by drainage, that which 
is of use to the plant is made much greater. 

Drainage prevents injury from drouth, for by means 
of it the plants are encouraged to make deeper root 



8o 



FIRST PRINCIPLES OF SOIL FERTILITY 



growth, and, hence, are not so easily affected by the 
extreme drying of the surface of the ground that takes 
place in times of scanty rainfall. It will readily be 
seen that tile draining determines the highest point the 
water-table can reach, but that in dry weather the level 
of the ground water my be much below the drain. It 
is sometimes thought, for this reason, that part of the 




Good drainage encourages the roots to strike downward and when the 
drouth comes the plants do not suffer 



water from summer rains, which would otHerwise be 
absorbed by the soil below the drain, may be lost 
through the tile. Experience has shown, however, that 
the water does not percolate into the drain as some 
suppose, and that it is only when the rainfall is suffi- 
cient to raise the water-table to the level of the drain, 
that any water is removed by it. It is a matter of 
common observation that, except in the case of quite 
low lands, it is only the very heavy summer rains that 



DRAINAGE AND IRRIGATION 



8i 



cause the drains to run. It will thus be seen that it is 
simply the excess of water which is removed by under- 
draining, and not that part which is of most importance 
to the plant. Although the crop probably makes little 
direct use of the free water, one must not lose sight of 
the fact that it may be drawn into the upper layers of 
the soil by capillarity to replace that lost by evapora- 



■#*>, 




Experiment to show how water is drawn to the surface from the lower 
levels of the soil by capillarity. (Drawn from photograph) 



tion, and for this reason the underdraining should not 
be so deep as to interfere seriously with capillary 
action. 

Drainage Sometimes Beneficial on High Lands. — 
Strangely enough, experience has shown that it is not 
merely low lying soils which are benefited by under- 
draining. In many cases heavy clay soils in elevated 
positions, especially if underlaid by rather impervious 
subsoils, are greatly improved in tilth by tiling. In 
such soils the percolation is so slow that practically 
the same efifect is produced as would be expected if 
the general level of the ground water were near the 
surface. These soils are made more mellow by drain- 



82 FIRST PRINCIPLES OF SOIL FERTILITY 

age and respond more readily to early tillage. Clay 
soils are often puddled by the fine particles in the soil- 
water being' deposited in the spaces between the soil- 
grains, thus cementing them together. The use of 
tile will often prevent this by causing the water to 
sink more rapidly through the soil. Tile-drained fields 
are not so likely to be injured by hauling heavy loads 
over them as are those not so treated. 

Irrigation in Humid Climates in Experimental 
Stage. — There are large areas in the western part of 
this country which, for lack of sufficient water, pro- 
duce very scanty vegetation, although in many in- 
stances the soil is well supplied with the other materials 
essential to the plant. The results to be derived from 
irrigation on such soils is too well known to call for 
comment here. The work of investigators, notably 
that of King, in the so-called humid climates east of the 
Mississippi has shown that even here the total rainfall 
is seldom sufficient for a maximum yield of the staple 
crops, and the precipitation is distributed so unevenly 
throughout the season that a comparatively small part 
of it can be used by the plants. 

Many market gardeners recognize the fact that some 
system of irrigation is necessary for the most profitable 
returns, and are in the habit of supplying water arti- 
ficially to their more valuable crops. Marshall P. 
Wilder when asked to name the three things most 
essential to successful strawberry culture is said to 
have replied: ''First, plenty of water; second, more 
water ; third, still more water." 

At the present time irrigation of the staple farm 
crops is not practiced to any large extent in the humid 



84 FIRST PRINCIPLES OF SOIL FERTILITY 

parts of this country. King has shown that the yield 
of these crops can be greatly increased by supplement- 
ing the rainfall with irrigation. Two examples will 
suffice : An average of two crops of potatoes gave an 
increase of 105 bushels per acre due to irrigation. In 
1894 he reports a crop of flint corn yielding 14.5 tons 
of dry matter per acre on an irrigated plot while the 
same corn yielded not more than 4 tons when receiv- 
ing only the natural rainfall. 




Increased yield of potatoes as a result of irrigation in humid climate (Wisconsin). 
The irrigated plots represented by the two piles on the right yielded 105 
bushels more per acre than the unirri gated on the left. (Drawn from half tone). 

It is more than probable that the future will see 
irrigation in extensive use east of the Mississippi, but 
at the present time it is only in the expermental stage, 
and it has yet to be demonstrated that it will be profit- 
able with ordinary crops under practical conditions. 
It is to be hoped that experiments along this line will 
soon be made, but they should be undertaken only by 
men who have made a study of the subject, for in 
humid climates irrigation in untrained hands may pro- 
duce more harm than good. 



CHAPTER VIII 

SUMMER FALLOWING 

Origin of Fallowing. — The practice of fallowing 
or "resting" the land is a very old one, being mentioned 
in the twenty-fifth chapter of Leviticus, where the 
people are commanded to rest the land every seventh 
year. 'The seventh year shall be a sabbath of rest 
unto the land." It is not known if this law was intro- 
duced into the Jewish code from a knowledge of the 
effect of fallowing on the soil, or if it had more to do 
with the mystical meaning that seems to be associated 
with the number seven in the Hebrew religion. 

A study of the history of agriculture leads one to 
believe that when the nomadic tribes first settled down 
to anything like systematic cultivation of the soil, they 
grew one crop (probably of the wheat family) con- 
tinuously on the same field, until the soil became so 
impoverished that it could no longer be tilled with 
profit. They then moved to other sections where vir- 
gin soil was to be found, and repeated the process. 
In the course of time it was discovered that these 
lands which had been abandoned would again produce 
good crops after a period of "rest" as it was called. 
This led to the practice of cropping the land one year, 
and allowing it to lie idle the next. It was later dis- 
covered that if the soil was frequently stirred during 
its resting period the growth the following year would 

85 



86 FIRST PRINCIPLES OF SOIL FERTILITY 

be much more luxuriant than if the ground was left 
undisturbed. From this beginning arose the practice 
of summer or bare fallowing as it is understood to-day. 
Later experimenters found that practically as good 
results could be obtained by the use of the so-called 
''fallow crops" in place of the year of rest. These 
are simply crops like Indian corn, turnips, potatoes, 
etc., which are intertilled and kept free from weeds 
during at least a part of their period of growth, and 
their introduction has practically done away with the 
use of the bare fallow in most localities. 

It is now well understood that what was formerly 
called resting the land is in reality a method of bring- 
ing about ideal conditions for the transformation of 
potential food into forms available to the plant. This 
practice of fallowing the land has practically fallen 
into disuse, but is being so strongly advocated in some 
quarters at the present time that it seems proper 
briefly to discuss the subject here. 

Fallowing adds nothing to the Soil. — The chief 
advantages claimed for summer fallowing are : ( i ) It 
makes plant food available, thus increasing the suc- 
ceeding crop. (2) It enables one to rid the land of 
weeds. (3) It destroys large numbers of injurious 
insects. It is doubtful, however, if under good con- 
ditions of tillage and soil management, fallowing is 
ever necessary. It adds nothing to the soil, but merely 
presents conditions that are favorable to the con- 
version of potential plant food into available forms ; 
and the increase in the crop following the fallow is 
seldom sufficient to recompense the farmer for the 
year of non-production. The crude methods of culti- 



SUMMER FALLOWING 



87 



vation in use in earlier times doubtless made fallows 
necessary, but the introduction of modern machinery, 




Diagram showing the construction of the lysimeter used at the New 
Yoric State Experiment Station to study the loss of nitrogen from the soil 
by leaching 

and more rational methods of tillage, have for the most 
part removed this necessity. 

There is no doubt of the efficiency of fallowing as 
a method of making plant food available, especially 
if the soil is frequently stirred. The conditions brought 
about by this treatment of the soil are just those 



88 FIRST PRINCIPLES OF SOIL FERTILITY 

which hasten nitrification, for it has been shown that 
the nitrifying bacteria thrive best in a warm, well 
aerated soil. The result of fallowing is, that during 
the hot summer months the process of nitrification 
goes on very rapidly, and as there is no growth to 
remove them, the nitrates accumulate in the soil in 
large quantities. 

Nitrogen May be Lost Through Fallowing. — At- 
tention has been called to the fact that the nitrates 
are easily leached out of the ground if present in any 
considerable amount. One of the dangers of the 
practice of fallowing is that if the land is left bare 
during the heavy rains of fall and winter, a large 
part of the nitrates formed during the summer months 
may be lost in the drainage water, a state of affairs 
that is to be avoided if possible. Snyder in a Minne- 
sota bulletin reports an experiment in which for every 
pound of nitrogen made available by fallow treatment, 
five pounds of total nitrogen w^as lost from the soil. 
At the New York Experiment Station at Geneva, 
tests were made to determine the loss of nitrogen in 
drainage water. Lysimeters were constructed to simu- 
late natural conditions as nearly as possible and yet 
allow the collection of the drainage water. Grass was 
grown on one of these lysimeters, being frequently 
mowed, as is done on a lawn. The soil in another 
was kept bare, no plants at all being allowed to grow, 
and the surface w^as frequently stirred. The drainage 
water from the lysimeters was all collected, and the 
nitrogen determined. It was found that in the case 
of the lysimeter on which the sod was growing, prac- 
ticallv no nitrogen was lost in the drainage water. 



SUMMER FALLOWING 89 

while in the other the loss of nitrogen amounted to 
from 218 to 357 pounds of nitrogen per acre each 
year. There is no doubt that these figures are in 
excess of the loss that would actually occur under 
field conditions, as the drainage in the lysimeters was 
perfect, and the effect of capillarity was probably less 




Sometimes the same forces which make soils destroy them as well. This granite 
knob was once covered with soil which has been washed away, probably as a 
result of the removal of the forest. 

than would have obtained in the field. They show, 
nevertheless, in a marked way the danger of great loss 
of nitrogen if the summer fallow is followed by heavy 
fall rains. In these experiments it was found that 
the loss was small in the summer months, nearly all 
of it occurring during the fall and winter. This loss 
of nitrogen amounts to from two to four times that 



90 FIRST PRINCIPLES OF SOIL FERTILITY 

removed by a crop of corn, and it will be remembered 
that it is the nitrogen which is in the form most avail- 
able to plants that is lost by leaching. 

Growing Crops Prevent Loss of Nitrogen. — These 
experiments are interesting also because they show how 
slight is the danger of loss of nitrogen if a crop is kept 
growing on the land. Numerous other experiments 
have confirmed this observation that if the field is 
covered with a growth of plants practically no nitrogen 
is lost in the drainage water, not because the nitrates 
are not formed but because the plants appropriate 
them as fast as they are produced. If then, the field 
which has been lying idle during the summer is 
planted to a crop before the fall rains begin, the loss 
of nitrogen will probably be prevented. The whole 
secret of preventing the waste of nitrogen from the 
soil is to have some crop on it during all the growing 
season. Nitrification takes place very slowly after 
the warm weather of summer has passed, so there is 
little danger of loss of nitrogen through leaving the 
ground bare in the late fall, provided a crop has been 
growing on it during the period that was f?vorable to 
nitrification. For this reason there need be no fear of 
loss of nitrogen as a result of fall plowing. 

Another Point of View. — There are, however, two 
sides to the question of the desirability of summer 
fallows. King cites experiments of his own which 
show (by determinations made April 30) that the 
plots which had been fallow the previous year con- 
tained 245 pounds more nitrate nitrogen per acre than 
the corresponding plots on which crops had been pro- 
duced. His experiments further showed that the 



SUMMER FALLOWING gi' 

amount of nitrate nitrogen in the fallow plots at that 
date was actually more than it was on August 22 of 
the year before. "From this it is clear that the crops 
on fallow ground start out in the spring under con- 
ditions very superior to those on the fields which had 
not been fallow." (King.) Unfortunately these ex- 
periments throw no light on the losses through drain- 
age, and it is impossible to decide whether this de- 
sirable condition in the spring has not been brought 
about by too great a drain on the total nitrogen supply 
of the soil. 

Summer fallowing has a tendency to conserve the 
moisture of the soil, as one can readily imagine when 
he recalls the rapid rate at which plants remove water 
from the ground. The tillage incident to the fallow 
also prepares an earth mulch and prevents loss of 
water by evaporation. At the Wisconsin Experiment 
Station it was found that in the spring following a 
summer fallow, the land which had been fallowed con- 
tained 203 tons more water per acre than did that 
which had been cropped the previous season. The 
following quotation is the closing paragraph of King's 
work entitled *'The Soil" : 

'Tn very wet climates or more especially in those 
which have heavy rainfalls outside the growing sea- 
son, so that excessive percolation and loss of plant 
food through drainage is large, summer fallowing in 
broad fields can not be recommended. But in dry 
countries, where the loss of plant food through drain- 
age channels is small, broad field summer fallowing 
may in some cases prove decidedly advantageous, be- 
cause with the deficient rainfall, there may not be 



92 FIRST PRINCIPLES OF SOIL FERTILITY 

moisture enough to mature a crop and at the same 
time to develop a sufficient store of plant food from 
the native fertility of the soil to meet the demands of 
the next season. At all events, the arguments urged 
against fallowing in countries like England do not 
apply to the semi-arid districts of the world with equal 
force." 

Need of Further Investigation. — This is one of 
the many problems in agriculture which calls for more 
thorough investigation and, fortunately, is receiving 
the attention of some of our experiment stations at 
the present time, so that more scientific data may be 
hoped for in the near future. The claim that fallowing 
is efficient in the destruction of weeds and injurious 
insects is a valid one, but the same results may pro- 
bably be obtained by a judicious rotation and by the 
use of cultivated crops, without allowing the ground 
to lie idle. After all, the practical question is whether 
the one crop after the fallow is equal to the two crops 
that would otherwise be produced, and the consensus 
of opinion among practical farmers seems to be that 
it is not. 

Short Fallows Desirable. — While the long summer 
fallow is to be recommended only when the soil has 
been abused and has become so foul with weeds that 
no other method will remove them, frequent use should 
be made of the short fallow {i. c. between crops). It 
will be found advantageous in many instances to plow 
the land immediately after the removal of one crop and 
keep it well stirred until the planting of the next. By 
this means loss of moisture from the soil is prevented 
and the decomposition of the organic matter is 



SUMMER FALLOWING 93 

hastened, so that a large supply of plant food is pre- 
pared for the succeeding crop. Barley or clover, for 
instance, is often followed by a fall planted grain with 
an interval of some weeks between the harvesting of 
the one and the planting of the other. If the field be 
plowed immediately after the first crop has been re- 
moved, and cultivated frequently, the results will be 
beneficial in starting the next crop with a larger supply 
of nitrates and moisture than would have been present 
if the ground had remained undisturbed. 

In the case of the fallow or cultivated crops pre- 
viously mentioned, the process of nitrification is ac- 
celerated between the rows as it is in the bare fallow, 
but the growing plants appropriate the nitrates almost 
as rapidly as formed, and hence prevent loss of nitro- 
gen in the drainage water. 



CHAPTER IX 

HUMUS AND GREEN MANURING 

Humus Necessary to Soil Fertility. — Loss of fer- 
tility in a soil is in a great number of instances due to 




The plants growing at the edges of lakes and streams retain the soil which 
is carried down from the adjoiing highlands. Sometimes muck or humus 
soils are formed in this way. 

the rapid decrease in the amount of humus which it 
contains. Humus is the product formed by the partial 
decay of organic matter, and is the material that gives 
the rich, black appearance to some soils. It is formed 
in most cases from the plants which have previously 
94 



HUMUS AND GREEN MANURING 95 

grown on the field, and have later beeonie a part of 
the soil. It may also arise from animal or vegetable 
materials added as manures. Virgin soils are com- 
paratively rich in humus, but investigation has shown 
that continued cropping with no provision for main- 
taining the supply of humus may result in its being 
decreased from one-third to one-half in a period of 
not more than 15 years. 

Humus is generally considered to be a necessary 
ingredient of fertile soils. To be sure, soils may be 
prepared containing no organic matter which will pro- 
duce good crops under artificial conditions where the 
water supply, etc., are under complete control. Under 
field conditions, however, a sufficient supply of humus 
is of paramount importance. 

Humus Increases Amount of Soil Water. — Humus 
increases the power of the soil to absorb and retain 
water, and, consequently a crop grow^i on a soil con- 
taining a fair amount of humus is less likely to sufifer 
from drouth. The following table giving the amount 
of water held in a cubic foot of the different varieties 
of soil illustrates this point. 

Pounds of zvatcr 
Kind of soil in one cubic foot 

Sand 27.3 

Sandy clay 38.8 

Loam 41.4 

Humus 50.1 

It will be seen that the quantity of water increases 
with the amount of humus present, the sand containing 
the least and the loam which has the largest percentage 
of humus, with the exception of the strictly humus 



96 



FIRST PRINCIPLES OF SOIL FERTILITY 



soil, containing much more. The organic matter in 
the high humus soils acts hke a sponge to absorb the 
water, but at the same time holds it in such condition 
that it is available to the crop. The peats are examples 




Organic matter increases the power of the soil to retain water, The soils in 
the glasses contain 0, 6, 12 and 20 per cent, of organic matter respectively 
from left to right. The tall cylinders show the relative amounts of water re- 
tained by the same weight of the soils. 



of extreme humus soils, and as is well known may 
hold more water than is desirable. 

Humus Improves Physical Condition of Soil. — 
Humus is also valuable in improving the ph3^sical con- 
dition of the soil. Sandy soils are made more com- 
pact by its presence and better able to supply the crop 
with moisture. Clay soils, on the other hand, are made 



HUMUS AND GREEN MANURING 



97 



more mellow by the addition of humus forming ma- 
terials. Clay is likely to become too compact unless 
there is a certain amount of organic matter present 
to prevent it from getting into this condition. In other 
words, humus forms loam, for a sandy loam is simply 
a sandy soil well supplied with organic matter, and a 




One of nature's methods of increasing the humus in the soil 



clay loam is clay which has been made light and mellow 
by the same material. 

Humus prevents extremes of soil temperature. A 
soil containing a sufficient supply of organic matter 
does not respond to changes of temperature so readily 
as one deficient in humus. The latter warms up some- 
what more slowly and retains its heat for a longer 
period. 

Humus a Storehouse for Plant Food. — Humus is 
of importance because it is a storehouse for plant food, 
especially for nitrogen. It has been shown that most 
of the nitrogen of the soil is present in the more or 



98 FIRST PRINCIPLES OF SOIL FERTILITY 

less decomposed organic matter. Besides the nitro- 
gen, the humus either contains phosphoric acid and 
potash in highly available forms or assists in ren- 
dering them available, for the crop is enabled to 
obtain much more of these substances from a soil 
rich in humus than from one in which the humus 
content is low. 

The presence of decomposing organic matter in 
the soil is an important factor in making the mineral 
elements of plant food available. During decay cer- 
tain acid substances known collectively as humic acids 
are produced, and these undoubtedly have a solvent 
action on the mineral matters of the soil, tending to 
make them more available to the plant. Perhaps quite 
as important a factor is the large amount of carbonic 
acid formed during the process of fermentation. This 
carbonic acid dissolved in the soil water is of prime 
importance in the production of soluble plant food, 
and it also has a beneficial effect on the physical con- 
dition of the soil, especially if the soil contains a large 
amount of clay. 

Experiments conducted in Minnesota and North 
Dakota have shown conclusively that as the humus 
content of the soil is decreased by constant cultivation 
and cropping (especially if planted continuously to 
one crop like wheat) the nitrogen content of the soil, 
the amount of moisture that it will retain, and the 
crop production are likewise decreased. 

Humus in Soil Decreased by Tillage. — All the 
methods for making potential plant food available 
which have been so far discussed tend to decrease the 
amount of humus in the soil. Tillage, drainage and 



HUMUS AND GREEN MANURING 99 

bare fallowing increase the amount of food available 
to the crop, because they present ideal conditions for 
the decomposition of the organic matter in the soil, 
but dependence upon these methods alone will even- 
tually result in injury through loss of humus. This 
fact is strikingly shown in the following table adapted 
from a Minnesota bulletin. 

LOSS OF NITROGEN AND HUMUS FROM SOIL 

Cultivated 
A' a five soil 23 years 

Total humus 3.97 2.59 

Total nitrogen 0.36 0.19 

Capacity to hold water . . . 62.00 54.00 

Humus Increased by Green Manuring. — The les- 
son to be learned from the above table is that while 
intelligent use should be made of improved methods 
of tillage, etc., these should be supplemented by some 
means of maintaining the supply of humus. The 
method that first suggests itself is Nature's own way 
of growing a crop to be afterwards incorporated with 
the soil. This is the process known as green manur- 
ing. Plowing under green crops raised for that pur- 
pose is one of the oldest means of improving the fer- 
tility of the soil. It was advocated by Roman writers 
more than two thousand years ago, and has been in 
more or less common use among progressive farmers 
ever since. 

The value of green manuring depends primarily 
upon the fact that it increases the amount of humus 
in the soil, a point that has been shown to be of great 
importance. 

LOFC 



lOO 



FIRST PRINCIPLES OF SOIL FERTILITY 



Two Classes of Plants for Green Manuring. — The 

crops used for this purpose may be of two kinds, viz: 
those which add nothing directly to the soil, and those 
which increase its nitrogen supply. Of the first class 
the crops generally recommended are buckwheat, 
spurry, mustard, rye, rape, etc. Plowing sod land 




Oats as a green-manure. Two classes of plants are used as green-manure— 
those which gather nitrogen and those whicn do not. Oats is u good example 
of the latter class. 



may be said to be a species of green manuring, and 
as such would be included in this class. These crops 
while they add no element of plant food to the soil 
are beneficial because they gather food from the soil 
that would not be available to the less hardy plants, 
and on their decay leave it in forms suitable to the 
succeeding crop. As mere humus formers they are 
of great value. 



HUMUS AND GREEN MANURING lOI 

The discovery that the leguminous plants can 
through the nodule forming bacteria fix the free ni- 
trogen of the air, has thrown a new light on green 
manuring, and the plants adapted to this purpose. 
The legumes have all the advantages of the other 
plants as humus formers, and at the same time in- 
crease the amount of nitrogen in the soil, and conse- 




Turning sod under is one method of green-manuring 

quently should be used for this purpose whenever 
possible. They are as a rule deeper rooted plants, 
and are supposed to bring up mineral food from the 
subsoil, and leave it where it will be within reach of 
the more shallow rooted plants. Of the legumes, 
the crops most often recommended are red clover, the 
lupines, cowpea, crimson clover, soy bean, the ordi- 
nary field bean and field pea; red clover being prob- 
ably the one most generally used. These plants have 
been found to produce good results even when the 



I02 FIRST PRINCIPLES OF SOIL FERTILITY 

crop was harvested, and the stubble only plowed under. 
At the Rothamsted Experiment Station it has been 
estimated that 50 pounds or more of nitrogen per acre 
is added to the soil in the roots and stubble of clover 
alone. 

Catch Crops for Green Manuring. — Where it is 
not advisable to. devote an entire season to the growth 
of a crop for green manuring, good results may often 
be obtained by growing "catch crops" between the 
profit crops. The use of cover crops on orchards, and 
as a protection to the land during the winter, are 
modes of green manuring. As far as possible legu- 
minous plants should be used for this purpose. The 
assertion is frequently made that by good tillage, and 
a judicious use of leguminous crops, the fertility of 
the soil may be maintained indefinitely without the use 
of fertilizers of any kind. The writer feels that this 
point has yet to be demonstrated, but no one doubts 
that these plants are of great value in the conserva- 
tion of fertility. 

Danger from Green Manuring. — While green ma- 
nuring is a valuable method of increasing the humus 
supply of the soil it is not unattended by danger. In 
a dry season, for instance, the growth of a crop to 
plow under may result in lowering the moisture con- 
tent of the soil to a point that is detrimental to the suc- 
ceeding crop. There is also danger in such a season 
that there may not be sufficient moisture in the soil 
to bring about the decomposition of the organic mat- 
ter which is turned under, resulting in serious injury 
to the physical condition of the soil. If a crop is 
plowed under during a dry season the ground should 



HUMUS AND GREEN MANURING 



103 



be rolled, or otherwise firmed, so as to renew capil- 
larity as far as possible. 

Green Manuring Not Advisable on Stock Farms. 
— Green manuring as a general practice is not to be 
recommended in any style of stock farming. The 




Crimson clover as an orchard cover-crop. The cover-crop is one method 
of green-manuring, and thejcrimsonclover is a good example of the nitro- 
gen-gathering plants used for this purpose. 



crops which are most valuable as green manures are 
also of great value as feeds, and it will be found more 
profitable to feed them to the animals and return the 
manure to the field, as will be shown later. On the 
whole, it may be said that green manuring will prove 
desirable in any system of farming (including truck 
farming) where the crops are sold from the farm, and 



I04 FIRST PRINCIPLES OF SOIL FERTILITY 

especially if all the crops produced are much alike in 
food requirements. On the other hand, if the farmer 
is engaged in animal husbandry the crops are of such 
great value as feeds that turning them under must be 
considered a wasteful practice. 



CHAPTER X 

ROTATION OF CROPS 

Origin of Rotations. — It is the common experience 
of farmers in those parts of the world where the land 
has been cultivated for a long time, that the fertility 
of the soil is maintained for a much longer time by 
grovv^ing a variety of crops instead of producing one 
crop continuously. The adoption of a system of rota- 
tion of crops has been the outgrowth of accident rather 
than the result of an understanding of its underlying 
principles. The system of alternating years of bare- 
fallow and wheat may be said to be a two year rota- 
tion and was the first to be adopted. History teaches 
us that this was later followed by a three year rotation 
consisting of fallow, wheat, beans or oats; and still 
later, when the value of clover and fallow crops be- 
came evident, this rotation gave way to the now famous 
Norfolk rotation of turnips, barley, clover and wheat, 
the typical English rotation. The Norfolk four year 
course represents the more common type the world 
over, consisting as it does of cereals alternating with 
hoed crops and leguminous crops. 

Plants Differ in Food Requirements.— There are 
many arguments to be advanced in favor of growing 
a variety of crops on the soil. The different crops vary 
in their food requirements and in their ability to pro- 
cure this food from the soil. Where one crop is grown 

105 



I06 FIRST PRINCIPLES OF SOIL FERTILITY 

continuously on the same field nearly all of the plant 
food available to that crop may become exhausted, 
while the soil would contain large quantities of food 
in forms that could be assimilated by plants of another 
class. Some crops evidently require the mineral mat- 
ter to be in a readily soluble form, while others can 
use "tougher" forms of plant-food. The early writers 
on agricultural chemistry supposed that the crop dur- 
ing its growth excreted substances that were injurious 
to itself, while they were at least harmless and perhaps 
beneficial to plants of a different class. This view is 
not now accepted, but it is believed that the failure to 
produce profitable results where one crop is grown con- 
tinuously is due to the exhaustion of the forms of plant 
food available to that particular crop. Some crops 
make an especial drain on one element of plant food. 
By growing crops with different food requirements 
there is less likelihood of any one element becoming 
exhausted and the different elements are more evenly 
used. 

Plants differ in Manner of Growth. — The various 
crops differ widely in their systems of root growth. 
Some plants like wheat are comparatively shallow 
rooted, and must obtain their food from the surface 
soil, others, as the clovers are very deep rooted, and 
are able to use food that would not be within reach 
of the more shallow rooted plants. The deep rooted 
plants can not only procure the low lying food, but 
probably bring a part of it to the surface where it re- 
mains upon their decay for the use of the succeeding 
crop. It is well known that the shallow rooted plants 
do better when preceded by a deep rooted crop. 



ROTATION OF CROPS lO/ 

Rotation Improves Soil and Economizes Labor. — 

When a variety of plants is grown the soil receives 
different treatment for each crop, so that the faults of 
one year are likely to be corrected the next, and for 
this reason, the soil is kept in much better physical 
condition. As a general rule the ground can be better 
prepared for the succeeding crop if a judicious rotation 
is practiced than if the same crop is grown continu- 
ously. The roots and stubble of clover and the grasses 
are also factors of some importance in improving the 
texture of the soil. Taken altogether the texture or 
tilth of the soil will be found to be much improved by 
rotation of crops. 

Where a variety of crops is grown on the farm it 
results in economy of labor, for the work of caring for 
them is distributed throughout the season instead of all 
coming at one time. In this way it makes it possible 
to secure cheaper and better help than where only a 
few kinds of plants are produced. 

Rotation Aids in Controlling Diseases, Insects, 
and Weeds. — Rotation also enables the farmer to con- 
trol plant diseases and to head off the injurious insects. 
Most of the plant diseases are caused by bacteria or 
other fungi wdiich live only on one genus of plants, or 
at any rate, are more or less restricted in the number 
of crops that they can use as host plants. Where one 
crop is grown continuously these disease-producing 
fungi are given every opportunity to be carried over 
from one year to another. Most of these germs are 
comparatively short lived, so that if three or four years 
of crops that are not suitable host plants intervene the 
germs are likely to be destroyed. In the same way 



Io8 FIRST PRINCIPLES OF SOIL FERTILITY 

it may be said that the injurious insects are Hmited to 
certain plants for their food supply, and if these plants 
are not grown on the field for a number of years the 
insects may die from starvation. These remarks do not 
apply, of course, to those insects which have migratory 
powers. There is no doubt, however, that both dis- 
eases and insects can be more easily suppressed if rota- 
tion is practiced. Where one crop is grown continu- 
ously the soil becomes infested with certain weeds 
which are not destroyed by the system of tillage nec- 
essary for that crop. The varying treatment to which 
a soil is subjected in a well planned rotation makes 
this condition impossible so that the destruction of 
weeds may be considered as one of the very desirable 
results of a rotation of crops. In lands badly infested 
with particular weeds it may even be desirable to omit 
from the rotation for a while the crop whose growth 
presents the best condition for their propagation. 

Effect of Rotation on Crop Production. — The 
effect of rotation on crop production is strikingly shown 
in the following table compiled from data furnished by 
the Rothamsted Experiment Station. 

EFFECT OF ROTATION ON CROP PRODUCTION AVERAGE 

OF EIGHT COURSES (32 YEARS) 

Bushels per acre 
Barley IV heat 

Grown continuously 18 12 

In rotation 32 26 

The rotation w^as the Norfolk rotation consisting of 
turnips, barley, clover and wheat, each grown one year, 
and the figures given are the average of eight crops 



ROTATION OF CROPS IO9 

each of barley and wheat, representing a period of 32 
years. The experiments with wheat and barley grown 
continuously on the same plot for 50 years have pre- 
viously been mentioned. For the sake of comparison 
the table gives the averages for the same eight years 
in which these crops were grown in rotation. All the 
crops were harvested and removed from the field, and 
as no manure of any kind was used it will be seen 
that the increased production of barley and wheat is 
a result of rotation solely. No stronger argument in 
favor of rotation of crops is necessary. 

Planning a Rotation. — Rotations are in use that 
cover periods of from two to seven years. In planning 
a rotation the farmer must be guided by his own condi- 
tions and requirements in the way of crops. A few 
general rules may be laid down, however. Every rota- 
tion should include at least one cultivated or hoed crop, 
such as corn, potatoes, etc., in order to receive the 
benefits of such a crop in the way of destroying weeds, 
improving tilth and setting free potential plant food. 
At least one leguminous crop should be included. The 
legumes are generally deep rooted crops, and in addi- 
tion to increasing the nitrogen supply of the soil, bring 
up plant food from the subsoil and leave it where it 
will be available to the succeeding crop. These deep 
rooted plants render the subsoil more porous and hasten 
its disintegration. A crop that is exacting in its food 
requirements should follow one that is less exacting, 
or in general terms, the crops should vary as much as 
possible in their food requirements, manner of growth, 
root system and the season of the year in which they 
occupy the ground. Whatever fertilizers are used 



no FIRST PRINCIPLES OF SOIL FERTILITY 

should be applied to the particular crop which will 
give the most profitable returns for their use. 

Resume. — In Part I the reader was reminded that 
continuous cropping without the use of fertilizers finally 
results in practical exhaustion of the soil. The food 
of the plant, and the history of the formation of the 
soil were briefly considered, and the conclusion was 
evolved that to maintain the fertility of the land two 
things were necessary ; first, to make more of the 
potential food available ; second, to add something to 
take the place of the materials removed in the crop. 

Part II has been devoted to a discussion of the first 
proposition. Tillage, drainage, irrigation, fallowing, 
green manuring and rotation are distinctly methods of 
changing potential plant food into available forms and, 
with the exception of the nitrogen gathered by the 
legumes, add no plant food whatever to the soil. Al- 
though, as has been previously stated, it is claimed 
by some that by an intelligent use of these processes 
alone a profitable yield can be obtained indefinitely, it 
is the common experience that even with the use of 
the best methods of culture known in the past, it is 
impossible to maintain the fertility of the land without 
the use of some form of fertilizers. As it is obviously 
impossible to return the crop to the soil, the next thing 
that suggests itself is to feed the crop to the farm 
animals and use their excrement as a fertilizer. The 
subject of barnyard manures is of sufficient importance 
to justify its discussion at some length as Part III 
of this treatise. 



PART III 
BARNYARD MANURE 



CHAPTER XI 

FACTORS AFFECTING THE VALUE OF 
FRESH MANURE 

Importance of Barnyard Manure. — Barnyard ma- 
nure is the oldest and is still undoubtedly the most 
popular of all fertilizers. It has stood the test of long 
experience, and has proven its position as one of the 
most important manures. The fact that the applica- 
tion of the excrement of animals to the soil results in 
increased crop production^ is mentioned by the early 
Roman writers, and from that time to the present, the 
majority of farmers have placed their main reliance 
on this class of manures for maintaining the fertility 
of the land. 

'*A well kept manure heap may be safely taken as 
one of the surest indications of thrift and success in 
farming. Neglect of this resource causes losses which, 
though little appreciated, are vast in extent. Waste of 
manure is either so common as to breed indifference, or 
so silent as to escape notice. 

"According to recent statistics there are in the United 
States in round numbers, 19,500,000 horses, m.ules, 
etc., 61,000,000 cattle, 47,000,000 hogs, and 51,600,000 
sheep. Experiments indicate that if these animals were 
kept in stalls or pens throughout the year and the 
manure carefully saved, the approximate value of the 
fertilizing constituents of the manure produced by 
each horse or mule annually would be ^2^, by each 

113 



114 FIRST PRINCIPLES OF SOIL FERTILITY 

head of cattle $20, by each hog $8 and by each sheep 
$2. The fertihzing vakie of the manure produced by 
the different classes of farm animals of the United 
States would, therefore, be for horses, mules, etc., 
$526,500,000 ; cattle $1,220,000,000 ; hogs $376,000,000 ; 
and sheep $103,200,000 or a total of $2,225,700,000. 

''These estimates are based on the values usually 
assigned to phosphoric acid, potash and nitrogen in 
commercial fertilizers, and are possibly somewhat too 
high from a practical standpoint. On the other hand, 
it must be borne in mind that no account is taken of 
the value of manure for improving the mechanical 
condition and drainage of soils, which as subsequent 
pages will show, is fully as important a consideration 
as its direct fertilizing value." (Farmers' Bulletin 192). 

If it is assumed that one-third of the value of the 
manure is annually lost by careless methods of man- 
agement, and this estimate is undoubtedly conserva- 
tive, the total loss from this source in the United States 
is about $750,900,000 ; a loss the more unfortunate be- 
cause practically all of it could be prevented. 

Composition of Manure From Different Animals. 
— The manures produced by the various classes of ani- 
mals differ greatly in their composition and in their 
physical properties. The table on the next page gives 
the average percentage composition of the fresh ma- 
nures (including solid and liquid excrement) from the 
more common farm animals. 

By reference to this table it is seen that the difference 
in the value of the manures as given is due, to a large 
extent, to the variation in the amount of water present 
in the excrement of the different classes of animals. 



FACTORS AFFECTING FRESH MANURE II5 

AVERAGE COMPOSITION OF FRESH MANURES ( WOLFF ) 



^t 



Sheep 
Horse 
Pig . . 
Cow . 
Mixed 







"« . 






|| 


2 "S 


11 


■<\ 


<-*\ 


^■^ 


•^ 


64.0 


0.83 


0.23 


0.67 


70.0 


0.58 


0.28 


0.53 


73.0 


0.45 


0.19 


0.60 


77.0 


0.44 


0.16 


0.40 


75.9 


0.45 


0.21 


0.52 



$3.39 
2..55 
2.14 
1.89 
2.08 



The moisture content also affects the physical proper- 
ties of the manure. Manures containing large amounts 
of water are "cold manures" ; that is they are manures 
which heat slowly because the amount of moisture pre- 
sent checks the fermentation. Sheep and horse ma- 
nures are known as "hot manures," and the more 
rapid heating of these when compared with pig or cow 
manure is probably due to their lower water content. 
The difference in the kind and quality of the feeds 
given to the various animals also affects the quality of 
the manure, as will be shown later. 

Amount and Value of Manure From Different 
Animals. — The figures given in the previous section 
show the comparative fertilizing value of the different 
animal excrements and are, therefore, of importance to 
one who is purchasing manures. For the farmer who 

* This valuation is based on 15 cents per pound for nitrogen, and 5 
cents for phosphoric acid and potash. This represents in round numbers 
the market price of these elements in commercial fertilizers at the present 
time. All the valuations given in the following pages will be on the same 
basis. 



Il6 FIRST PRINCIPLES OF SOIL FERTILITY 

produces manure to use on his own land, it is more 
important to know the total amount and value of the 
manure produced in a year by the different classes of 
animals. In the quotation above from Farmers' Bulle- 
tin 192 the approximate value of the manure produced 
per head by the ordinary farm animals is given. A 
fairer way to present the matter is to calculate the 
manure to the same live weight of the different animals. 
The following table compiled from Cornell Bulletin 
56 appears in Farmers' Bulletin 192. 

AMOUNT AND VALUE OF MANURE PER I, GOO POUNDS OF 
LIVE WEIGHT OF DIFFERENT ANIMALS 

Amount Value Value 

per day per day per year 

pounds cents dollars 

Sheep 34.1 7.2 26.09 

Calves 67.8 6.7 24.45 

Hogs 56.2 10.4 37.96 

Cows 74.1 8.0 29.27 

Horse 48.8 7.6 27.74 

If the figures given in this table are accepted as 
representing normal conditions, it follows that, making 
proper allowance for the proportion of the different 
kinds of animals found on the ordinary farm, the sum 
of thirty dollars may be taken as the average value of 
the fresh manure from each 1,000 pounds of live 
weight. The use of this factor (thirty dollars per 
1,000 pounds) will enable the farmer to calculate ap- 
proximately what the nitrogen, phosphoric acid and 
potash in the manure produced on his farm would 
cost if purchased in commercial fertilizers, granting 



FACTORS AFFECTING FRESH MANURE 



117 



that the manure is so managed as to prevent loss of 
its vakiable constituents. 

Value of the Manure Determined by the Ration. — 
The total value of the manure produced by a given 
number of animals is dependent on the quality, and 
quantity of the feeding stuff used in the ration. That 
the different materials used for feeding vary greatly in 
their fertilizing value is clearly shown in the following 
table, which gives the quantity of fertilizing materials 
in one ton of a few of the common feeding stuffs. 



Corn meal . . . 
Corn silage . . . 
Corn stover . . 
Clover hay . . . 
Gluten meal . . 
lyinseed meal . . 
Cotton-seed meal 
Meat scraps . . 

Oats 

Timothy hay . . 
Wheat bran . . 
Wheat straw . 



1^ 


1^ 


11 

SI 


36.4 


14.0 


8.0 


5.6 


2.2 


7.4 


20.8 


5.8 


28.0 


41.4 


7.6 


44.0 


100.6 


§.6 


1.0 


108.6 


33.2 


27.4 


135.8 


57.6 


17.4 


194.0 


126.0 


14.0 


41.2 


16.4 


12.4 


25.2 


10.6 


18.0 


53.4 


57.8 


32.2 


11.8 


2.4 


10.2 



■^ s 

-^■2 



$6 56 

1.32 

5.81 

8.79 

15.44 

19.22 

23.20 

36.10 

7.62 

5.21 

12.. 52 

2.40 



The figures given in the above table represent the 
fertilizing values of the different feeds, provided they 
are used directlv as manures. It is evident that the 



Il8 FIRST PRINCIPLES OF SOIL FERTILITY 

richer the ration is in nitrogen, phosphoric acid and 
potash, the more vakiable will be the manure produced 
by the animal. The next question to determine is what 
proportion of the fertilizing content of the food is 
recovered in the excrement. 

No Loss of Plant Food With Mature Animals.— 
Let the reader imagine that a matured animal (a steer 
for instance) is confined in such a manner that all of 
the excrement, both liquid and solid, can be preserved, 
and that the animal is kept on a maintenance ration. 
If now the total dry matter in the materials fed is 
determined, and likewise that voided in the excrement, 
it will be found that the dry matter in the excrement 
is just about one-half the amount that was present in the 
food consumed, the greater part of the other half hav- 
ing been given off from the lungs as carbonic acid gas. 
If, on the other hand, the food is analyzed to determine 
the nitrogen, phosphoric acid and potash it contains, 
and the excreta are also examined, in the same way, 
it will be found that the entire amount of these con- 
stituents is voided by the animal in the solid and liquid 
excrement. While the excreta, therefore, contain only 
half of the total dry matter which was present in the 
ration, they contain all the constituents that are gener- 
ally considered to have fertilizing value. 

Young Animals Retain Part of Plant Food. — 
While these figures would hold good for a matured 
steer that was neither gaining nor losing in weight, 
they are not correct for young and growing animals. 
The latter retain a certain proportion of the nitrogen 
and phosphoric acid for use in building up their bodies. 
The amount thus retained depends primarily on the 



FACTORS AFFECTING FRESH MANURE II9 

age of the animal, and also as will readily be imagined, 
on the rapidity of its growth. Recent experiments indi- 
cate that calves during the first three months of their 
lives retain in their bodies about one-third of the fer- 
tilizing value of the food consumed, or in other words, 
the excrements from such animals contain two-thirds 
of the fertilizing ingredients of the ration. For the 
first year of their existence they use in body growth 
an average of about one-fifth of the nitrogen, phos- 
phoric acid and potash that was present in the food, 
and the amount gradually diminishes until practically 
not any of these materials are retained. It may be 
noted here that where matured animals are gaining in 
weight during fattening there is no drain on the fer- 
tilizing value of the manure, provided the gain in 
weight is all in fat. This is due to the fact that fat 
contains only carbon, hydrogen and oxygen, and hence 
its production does not remove any of those constitu- 
ents which are considered in calculating the fertilizing 
value. Although the steer and calf have been used 
by way of illustration, the remarks regarding them 
hold true as well of the other classes of animals such 
as swine, sheep and horses, and the age of the animal 
has the same efifect on the value of the manure. 

The Milk Contains Some Plant Food.— In the case 
of the cow another factor is introduced, as a certain 
proportion of the nitrogen, phosphoric acid and potash 
is removed in the milk. Milk contains on an average 
about 0.53 per cent of nitrogen, 0.19 per cent of phos- 
phoric acid and 0.175 per cent of potash. A cow giving 
an annual yield of five thousand pounds, therefore, 
removes in the milk fertilizing materials amounting in 



120 FIRST PRINCIPLES OF SOIL FERTILITY 

value to $4.89. If the milk is sold this amount of 
fertility is removed from the farm. If, on the other 
hand, butter only is sold practically none is carried 
away, as all the valuable ingredients are found in skim- 
milk ; the fertilizing value of three hundred pounds 




Butter removes a smaller quantity of the elements of fertility than any other pro- 
duct which ts sold from the farm. The fertilizing value of one ton of butter 
amounts to only 44 cents. 

of butter, for instance, amounting to only 6^ cents. 
Even where the milk is removed fully 85 per cent of 
the manurial value of the food is recovered. 

Eighty Per Cent of the Plant Food Recovered in 
Manure. — It will thus be seen that a very large part 
of the elements of fertility contained in the ration fed 
is recovered in the excreta, and that the age of the 
animal is the principal factor in determining the 
amount that is removed. The fertility removed in the 
milk when it is sold from the farm is also of considera- 
ble importance, and should not be ignored. Taking 
into account the relation between matured and young 
stock, milch cows and non-milk producing animals, as 
found on the average farm, it is conservative to assume 



FACTORS AFFECTING FRESH MANURE 121 

that at least 80 per cent of the nitrogen, phosphoric 
acid and potash, present in the materials fed on the 
farm, is voided by the animals in the solid and liquid 
excrement. This takes into consideration the amount 
removed in the milk, that retained by the young ani- 
mals during their growing period, and, consequently, 
the fertility removed from the farm by the sale of the 
animals produced thereon. In order, then, to deter- 
mine the fertilizing value of the excrement produced 
from a ton of any of the feeding stuffs mentioned in 
the table given above it is only necessary to find eighty 
per cent of the fertilizing value therein stated. It will 
thus readily be seen that the composition of the feed- 
ing stuff really determines the value of the excrement. 
That produced from one ton of wheat straw being 
worth only $1.74, while the excrement from one ton of 
corn meal, wheat bran, linseed meal or cottonseed meal 
would be worth $4.53, $9.84, $15.49 and $20.93 ^^~ 
spectively. 

Nitrogen the Most Valuable Constituent of Ma- 
nure. — By referring to the table it is seen that the most 
important factor in determining the fertilizing value 
of a feeding stuff, or the manure produced from it, 
is the amount of nitrogen that it contains. This is due 
to the fact that nitrogen is usually present in larger 
proportion than phosphoric acid or potash, and is much 
more costly vvhen purchased. Nitrogen is also used 
by the animal body in much larger amounts than the 
other substances, and the difference in fertilizing value 
between the food and the excrement is largely due to 
the retention of nitrogen. It will be shown that the 
losses in manure fall more heavily on its nitrogen con- 



122 FIRST PRINCIPLES OF SOIL FERTILITY 

tent than on the other elements, so it again becomes 
evident that the most expensive material to furnish is 
also the one most readily lost. This but confirms a 
previous statement that the problem of the profitable 
maintenance of fertility is largely a question of an 
economic method of supplying the plant with nitrogen. 
Effect of Ration on Value of Manure Per Ton. — 
While the total value of the excrement depends almost 
entirely on the composition of the ration, it does not 
follow that the value of the manure per ton is propor- 
tional to the fertilizing value of the substances fed. 
Cattle fed on highly nitrogenous rations drink more 
water than those kept on a ration low in nitrogen, and 
experiments have shown that the excrement contains 
a larger per cent of water in the former case than in 
the latter. The cattle fed on the narrow ration will 
produce more tons of excrement at a greater total 
value, but the value per ton will not be very different 
from that resulting from a wider ration. The follow- 
ing table adapted from a Cornell bulletin gives results 
with two lots of pigs, Lot I, having been kept on feeds 
extremely high in nitrogen, while Lot II, were given 
a ration containing a much smaller proportion of nitro- 
genous materials. 

EXCREMENT FROM I,000 POUNDS LIVE WEIGHT OF PIGS 

Weight per Value per Value per 

day, lbs. day ton 

Lot I .... 108.9 $0.2106 $3.86 

Lot II .... 56.2 0.104 3-66 

It is noteworthy that while the total value of the 
manure produced per 1,000 pounds of live animal in 



FACTORS AFFECTING FRESH MANURE 1 23 

Lot I was twice that of Lot II, there is very httle 
difference in the value per ton, due to the fact that 
the weight of excrement produced in the first case was 
nearly twice that in the latter. 

Effect of Bedding on Value of Manure.— The fac- 
tors just discussed are those which affect the value of 
the excrement. The term barnyard manure as it is 
generally used includes the excreta and the litter or 
bedding used to absorb the urine. The following table 
gives the composition of some of the materials used 
for bedding. 

FERTILIZING CONSTITUENTS IN ONE TON OF LITTER 

Nitrogen Phos. acid Potash 

pounds pounds pounds 

Wheat straw .... 9-6 4-4 12.6 

Oat straw 9-2 5-6 35-4 

Clover straw .... 29.4 8.4 25.2 

Sawdust 4.0 6.0 14-0 

Peat 20.0 

It is evident that the total fertilizing value of the 
manure is the sum of the value of the excrement and 
the bedding, and the richer the bedding is in fertiliz- 
ing constituents the more valuable will be the manure. 
The materials used for bedding are in most cases rather 
low in the elements of fertility so that the use of large 
amounts of bedding decreases the worth per ton of the 
manure, but in any case sufficient litter should be used 
to absorb all of the liquid excrement. 

Calculating the Amount of Manure From the Ra- 
tion. — It is often of great interest and importance to 
the farmer to be able to calculate approximately the 



124 FIRST PRINCIPLES OF SOIL FERTILITY 

amount of manure that will be produced from the 
materials fed to his animals, as well as its value. Var- 
ious estimates of the amount of manure produced by 
the different classes of animals have been made from 
time to time, but it will be much more satisfactory to 
use the ration as a basis for calculation. The total 
weight of manure may easily be computed in this way 




A way in which plant food is often wasted. If the straw is not used for feed or 
bedding it should at least be scattered 

and the figures derived are remarkably close to the 
average results as determined by experiment. 

It has been stated that 50 per cent of the dry matter 
present in the ration is recovered in the excrement. 
Experience has shown that the least amount of bedding 
that will absorb all of the urine excreted by the animal 
must contain dry matter equal to 25 per cent of the 
dry matter in the feeding stuffs used. Hence, if the 
assumption is made that just sufficient bedding is used 



FACTORS AFFECTING FRESH MANURE I25 

to absorb all of the liquid excrement it is seen that 
the manure (excrement plus bedding) contains 75 per 
cent as much dry matter as was contained in the ration. 
According to the table on page 115, mixed farm ma- 
nures contain on the average 75 per cent of water, or 
only 25 per cent of dry matter, so that the 75 per cent 
of dry matter mentioned above as occurring in the 
manure, must be multiplied by four to find the total 
of manure. This gives a result of 300 per cent of 
the dry matter in the ration for the weight of the 
manure produced therefrom. It will thus be seen that 
to calculate the amount of manure resulting from the 
use of any given food materials it is only necessary 
to multiply the weight of the dry matter in the ration 
by three. This method of computation may perhaps 
be made plainer by an example. Let it be assumed 
that a mixture of feeding stufifs is used which contains 
1,200 pounds of dry matter. The excrement produced 
by feeding this ration would contain 600 pounds of 
dry matter. In order to absorb all of the urine voided 
by the animal, straw, or some other bedding material 
must be used in an amount large enough to supply 300 
pounds of dry matter. Now, as the manure is com- 
posed of the excrement plus the bedding it follows 
that the manure contains 900 pounds of dry matter. 
Only 25 per cent, of the manure is dry matter, so that 
the 900 pounds of dry matter in the example represents 
one-fourth of the total weight of the manure. The 
manure, therefore, weighs 3,600 pounds, which is just 
three times the dry matter that was present in the 
ration assumed. 

This method of calculating the manure by multiply- 



126 FIRST PRINCIPLES OF SOIL FERTILITY 

ing the dry matter in the ration by three holds true, 
of course, only when the theoretical amount of bedding 
is used. In actual practice the farmer uses all of the 
bedding materials he has at hand even though in ex- 
cess of the amount required to absorb the urine, and 
it is generally considered advisable to do so, for the 
bedding materials decay much more readily when 
mixed with the excrement of animals. In the best 
farm practice where the greatest possible use is made 
of all substances suitable for feeding there is seldom 
an excess of bedding materials. In case more litter 
than the theoretical amount is used the method of cal- 
culation given above must be corrected by adding to 
the total, the weight of the bedding in excess of 25 per 
cent of the dry matter in the ration. If in the exam- 
ple, for instance, instead of using 300 pounds of straw 
500 pounds had been used as bedding, the total weight 
of the manure would have been 3,800 pounds. 



CHAPTER XII 

AMOUNT AND VALUE OF THE MANURE 
PRODUCED ON A FARM 

Value af Manure Little Appreciated. — The great 
value of barnyard manure as a farm resource is appre- 
ciated by very few farmers. Its importance is doubt- 
less realized to a greater extent at the present time 
than ever before, but even now a large proportion of 
those engaged in agricultural pursuits seem to have 
little realization of the immense loss incurred through 
the waste of this important product of the farm. In- 
deed many farmers apparently look upon the manure 
as one of the necessary nuisances of a system of animal 
husbandry, and begrudge the time and labor required 
to remove it from the barn and feeding lot. Barns 
have been erected on the banks of swift running 
streams with the express purpose of emptying the ma- 
nure into the creek, in order that it may be removed 
with the least possible expenditure of labor. While 
these cases are extreme the reader has only to look 
around him as he travels through the country to see 
practices which fall only a few degrees short of this 
in the matter of wastefulness, due either to lack of 
knowledge of the value of the manure or to an indiffer- 
ence that is even more lamentable than ignorance. 

Manure From Fifty Cows. — In order that the great 
fertilizing value of the manure produced on the farm 
may be more definitely shown as well as to make more 

127 



128 FIRST PRINCIPLES OF SOIL FERTILITY 

clear the methods of calculation described in the pre- 
vious chapter, figures are given here for the food con- 
sumed and the amount and value of the manure pro- 
duced in one year by a herd of 50 dairy cows, giving 
an average yield of 15 pounds of milk daily. For the 
sake of simplifying the calculations and statements of 
results it is assumed that the same ration is fed through- 
out the year. In actual practice, of course, the ration 
varies somewhat at different times of the year, but 
as the experienced feeder aims to keep approximately 
the same relation between the concentrates and rough- 
age, and, as nearly as may be, the same ratio between 
proteids and carbohydrates, the results of this compu- 
tation from a single ration will not be very different 
from those which would be derived from a variety, 
each having about the same nutritive value. 

The Ration Used. — It is desired to make this esti- 
mate conservative and for this reason no feeds are 
included that are unusually high in fertilizing constitu- 
ents. The following ration will be used as a basis for 
the calculation : 

Daily ration for a cow weighing 1,000 pounds and 
giving 15 pounds of milk per day; 10 pounds of a mix- 
ture of one-third each of cornmeal, ground oats, and 
bran; 35 pounds of corn silage; 15 pounds of clover 
hay (medium red). 

This combination has been recommended by a promi- 
nent authority on the feeding of animals as a good 
ration for practical feeding, and one which will meet 
with the approval of conservative dairymen. At the 
same time the ration is well balanced, and will con- 
form reasonably well to the best feeding standards. A 



AMOUNT AND VALUE OF MANURE PRODUCED I29 

great manv people use a higher feeding standard than 
is represented by this ration so on the whole it may 
be said that the results of this calculation certainly are 
not higher than the average for good dairy condi- 
tions. It will be assumed that just the amount of wheat 
straw which would theoretically be necessary to absorb 
the liquid excrement is used as bedding. 

The following table gives the dry matter and ferti- 
lizing constituents in each i,ooo pounds of the different 
materials. 

DRY MATTER AND FERTILIZING CONSTITUENTS IN I,000 
POUNDS 



Corn meal 
Oats . . . 
Bran . . . 
Silage . . 
Clover . . 
Straw . . 



^ 




1 








5: s 


11 


SI 






•^ 5 


- a 








> -c^ 


s:^ 


671 


15.8 


6.3 


8S9 


18.6 


7.7 


883 


26.7 


28.9 


220 


2.8 


1.1 


887 


20.7 


3.8 


875 


4.8 


2.2 



« 5 



4.0 

5.9 
16.1 

3^7 
22.0 

6.3 



Fertility in the Excrement. — The ration mentioned 
above represents the amount of the different sub- 
stances fed to each cow per day. This amount must 
be multiplied by 50 and then by 365 to determine the 
total amount fed per year. From the totals thus ob- 
tained and by the use of the table just given it is 
possible to calculate the dry matter and fertilizing con- 



130 



FIRST PRINCIPLES OF SOIL FERTILITY 



stituents of the entire amount. of food given to the fifty 
cows during the year. These results are compiled in 
the following table. 



TABLE SHOWING TOTAL AMOUNT OF MATERIALS FED 
WITH DRY MATTER AND FERTILIZING CONSTITUENTS 





s a 




1-3 




II 


Cornmeal 


60,830 

60,830 

60,830 

638,750 

274,250 


52,982.9 

54,077.8 

53,712.9 

140,525.0 

239,968.7 


967.11 
1,141.34 
1,624.16 
1,788.50 
5,676.88 


383.23 
468.39 

1,757.98 
702.63 

1,042,15 


243.33 


Oats 


358 90 


Bran 


979 36 


Silage 

Clover 


2,363.38 
6,033.50 




Totals 


1,095,490 


541,267.3 


11,197.99 


4,354.38 


9,978.46 



While the totals given in the table show the amounts 
of fertilizing constituents in the feeding stuffs used 
during the year it will be remembered that only eighty 
per cent of this amount is recovered in the excrement. 
The solid and liquid excrement combined, therefore, 
contain of nitrogen 8958.47 pounds, phosphoric acid 
3483.50 pounds and potash 7982.77 pounds. 

Fertility in Bedding Must be Added. — The ma- 
nure, however, contains the fertilizing constituents of 
the bedding in addition to that found in the excrement. 
It has been stated that the least amount of bedding 
that will absorb the urine must contain dry matter 
equivalent to one-fourth the dry matter in the ration. 



AMOUNT AND VALUE OF MANURE PRODUCED I3I 

The dry matter in the bedding used in this example, 
therefore, must amount to 135,316.8 pounds. To fur- 
nish this quantity of dry matter it is necessary to use 
at least 154,647.7 pounds of wheat straw. If the 
amount of nitrogen, phosphoric acid and potash in 
this weight of straw are added to that in the excrement 
the results will express the quantities of these ingredi- 
ents found in the manure. The following table gives 
these data : 

FERTILIZING CONSTITUENTS OF THE MANURE 

Nitrogen Phos. acid Potash 

pounds pounds pounds 

In excrement . . 8958.47 3483-50 7982.77 

In bedding . . . 742.61 340.22 974-28 

Totals . . . 9701.08 3823.72 8957.05 

Value of the Manure. — The prevailing prices of 
fertilizing materials at the present time as given by 
the eastern experiment stations are such that the pur- 
chaser pays at the rate of about 15 cents per pound for 
nitrogen, and 5 cents each for phosphoric acid and 
potash. These prices hold only when crude materials 
are bought and much higher prices are paid for mixed 
fertilizers. To determine the value of the manure pro- 
duced by the 50 cows it is only necessary to multiply 
the totals in the last table by the trade prices of the 
constituents. These calculations are given below : 

VALUE OF MANURE FROM 50 COWS 

Value of nitrogen $1,455.18 

Value of phosphoric acid 191. 19 

Value of potash 447-85 

Total value of manure 2,094.22 



132 FIRST PRINCIPLES OF SOIL FERTILITY 

This means that the fresh manure from the 50 cows 
contains amounts of nitrogen, phosphoric acid and 
potash that would cost the farmer at least $2,094.22 if 
purchased in commercial fertilizers. How nearly the 
actual agricultural value of the manure will approach 
the trade value depends upon a number of conditions 
such as the crop to be fed, the physical condition and 
tilth of the soil, the climatic conditions and above all 
the intelligence displayed in its care and use. The 
same statements apply to commercial fertilizers, the 
trade price not necessarily being any indication of the 
agricultural value of the material, and there is no doubt 
that the farmer who receives the best returns from 
commercial fertilizers is also the one who will be best 
repaid for the use of barnyard manure. Whatever the 
reader's opinion may be of the actual value of manure, 
the figures evolved in this calculation must impress 
him with the fact that his manure heap is a valuable 
resource, and that he cannot afford to waste so valua- 
ble a substance even if it is but a by-product of the 
farm. 

Amount of Manure and Value Per Ton. — It will 
be interesting to carry these calculations a little further 
and determine the total amount of manure produced 
and the value per ton. It has been shown that the 
weight of the manure is three times the weight of the 
dry matter in the ration. The total dry matter fed 
during the year was found to be 541,267.3 pounds so 
the manure would weigh 1,623,801.9 pounds or 81 1.9 
tons. The total value of the manure divided by the 
number of tons gives $2.58 as the value of a ton of 
the manure. In this connection it is interesting to 



AMOUNT AND VALUE OF MANURE PRODUCED 133 

note that in field experiments conducted for ten years 
at the Ohio Experiment Station, the average value of 
the increase of crop produced by one ton of fresh ma- 
nure amounted to $344. If 50 cents per ton is allowed 
as the cost of applying the manure to the field there 




A very wasteful method of handling a valuable product. Such a barnyard 
must result in great loss of fertility 

ctiU remains a handsome profit as a result of the ap- 
plication. 

A Profitable Calculation.— The easiest way for the 
farmer to calculate the value of the manure produced 
per year on his farm is to add together the amounts of 
fertilizing constituents in all the feeds fed to the var- 
ious animals, take 80 per cent of this, and add to it 
the fertilizing constituents of the bedding, and multi- 
ply the totals by the trade prices per pound for nitro- 



134 FIRST PRINCIPLES OF SOIL FERTILITY 

gen, phosphoric acid and potash. If the reader will 
take the trouble to do this for his own farm, using 
the table at the back of this book to find the fertilizino- 
constituents in his crops, he will find the results ex- 
tremely interesting, and will be well repaid for his 
labor, in the better understanding that he will have of 
his farm resources. 

How to Increase the Value of the Manure. — It 
often occurs that the farmer finds it necessary for one 
reason or another to supply more plant food to the 
soil than can be obtained from the manure produced 
from the crops raised on his farm. Under these cir- 
cumstances, if he is engaged in animal husbandry, he 
will find that the most economical way to increase the 
plant food is by purchasing feeding stuffs rich in the 
fertilizing constituents, feeding them to his animals 
and using the manure as a fertilizer. The most suc- 
cessful stockmen find it profitable to reinforce the feeds 
raised on the farm with one or more of the various 
mill and other by-products that are sold as cattle feeds. 
A glance at the table on page 117 will immediately 
suggest how easily the value of the manure might be 
increased at the same time that the ration was being 
materially improved. It will readily be seen that the 
purchase of a relatively small quantity of some of the 
concentrated feeding stuffs would more than replace 
the 20 per cent of fertilizing value of the crops lost 
during feeding. The farmer who buys large quanti- 
ties of concentrates is increasing the fertility of his 
land provided he is taking proper care of the manure. 
In purchasing feeding stuffs one should always con- 
sider their fertilizing value as well as the feeding value, 



AMOUNT AND VALUE OF MANURE PRODUCED I35 

for, while the substance is bought primarily to feed, it 
is sometimes possible to buy two different materials 
which will serve practically the same use as feeds, and 
yet vary greatly in their values as fertilizers. Even 
where a number of animals sufficient to consume all of 
the crops raised on the farm is at hand it is often 
advisable to sell some of the products, and use the 
money thus obtained for the purchase of other feeding 
stuffs. There is scarcely a farm on which such an ex- 
change could not be made to advantage, both from the 
feeding standpoint, and in order to increase the value 
of the manure. A study of the market prices of the 
various farm products and concentrates in any year 
will readily show how such exchanges could be made at 
a profit to the farmer. To illustrate what is meant by 
this statement the following simple example recently 
used by the writer in one of his classes is given. 

At the time mentioned it was possible to buy on the 
local market seven tons of clover hay for the price of 
five tons of timothy hay, and five tons of corn could 
have been exchanged for six tons of bran. The prob- 
lem w^as to determine the increase in fertilizing value 
due to such an exchange. Calculating the value of the 
different materials in the manner already described the 
results may be briefly stated as follows 

Fertilizing value of 7 tons of clover . . . $52.85 
Fertilizing value of 6 tons of bran .... 73.80 

Total 



Fertilizing value of 5 tons of timothy 
Fertilizing value of 5 tons of corn . 

Total 

Gain due to exchange 



$126.65 

$23.00 
28.30 

$51.30 
$75.35 



136 FIRST PRINCIPLES OF SOIL FERTILITY 

By a simple exchange of products without any cash 
outlay the fertilizing value of the ration would have 
been increased $75.35, and consequently the manure 
produced would have been worth $60.28 more than that 
resulting from the use of the corn and timothy hay. 
The increase in value of the manure does not tell all 
of the story, for the total weight of food has been 
increased nearly one-third. Its actual feeding value 
has been increased more than one-third, due to the 
larger amount of proteid in the ration. It is well 
known that cattle require less weight per head of a 
narrow ration than of one that is more carbonaceous. 
This example is cited merely as a suggestion of the 
possibilities of exchange. A little careful considera- 
tion will show that such exchanges may be made of 
great practical value. 

The value of manure is affected by the quantity of 
food given the animal as well as by the quality. Other 
things being equal the manure from animals fed lib- 
erally will be more valuable than that from those that 
are fed insufficiently. This is mainly due to the fact 
that the latter use a larger proportion of the nitrogen 
of the food and hence the percentage returned in the 
manure is smaller. Liberal feeding then produces 
richer manure. 



CHAPTER XIII 



LOSSES IN MANURE 



Relative Value of Solid and Liquid Excrement.— 

The great possibilities of barnyard manure as a means 
of supplying nitrogen, phosphoric acid, and potash to 
the soil have been discussed at some length. While 
values equal to those mentioned may be realized by 
any farmer by the exercise of reasonable care, the fact 
remains that few even approximate these results with 
their present practices. Barnyard manure is a perisha- 
ble material, and must be handled with care and intel- 
ligence to obtain its maximum value. As manure is 
handled on the majority of farms to-day it is doubtful 
if half its worth is realized. The greatest loss that is 
likely to occur is the waste of the liquid excrement 
through the use of insufficient bedding to absorb it. 
The urine is really the most valuable part of the ex- 
crement, and unless plenty of bedding is used the value 
of the manure will fall far below that given in the 
previous chapter. Apparently few people realize the 
importance of using plenty of litter, for it is not 
unusual to see barns constructed in such a way as to 
cause the urine to run off as rapidly as possible. Doubt- 
less the reader has before now seen holes bored in the 
barn floor to keep the floor dry by draining off the 
liquid excrement. The following table gives the com- 
position of the solid and liquid excrements : 

137 



138 



FIRST PRINCIPLES OF SOIL FERTILITY 



PERCENTAGE OF FERTILIZING CONSTITUENTS IN SOLID 
AND LIQUID EXCREMENTS 





Nitrogen 


Phos. 


acid 


Soda and Potash 




Solid 


Liquid 


Solid 


Liquid 


Solid 


Liquid 


Horses 


0.50 


1.20 


0.35 


trace 


0.30 


1.50 


Cows 


0.30 


0.80 


0.25 


trace 


0.10 


1.40 


Swine 


60 


0.30 


0.45 


0.125 


0.50 


0.2 


Sheep 


0.75 


1.40 


0.60 


0.05 


0.30 


2.0 



The table shows that considered pound for pound 
the Hquid excrement is more valuable than the solid, 
except in the case of the swine. As the relative weights 
of solid and liquid excrement produced by the animals 
are not given it does not show the real proportional 
value of the liquid and solid excrement produced from 
a given ration. Several experiments have been made 
to determine this point, and there is a wide variation 
in the results. It is perfectly safe to say, however, that 
of the total fertilizing materials found in the manure 
two-thirds of the nitrogen, and four-fifths of the pot- 
ash are found in the urine, but practically none of the 
phosphoric acid. The solid part then contains only one- 
third of the nitrogen, one-fifth of the potash, and nearly 
all of the phosphoric acid. It will thus be seen that 
a little over half of the total value of the manure is 
in the urine. In the example mentioned in Chapter 
XII, if the liquid excrement had been allowed to run 
away the. value of the manure would have been less 
than $900.00 instead of $2,049.00 as calculated. 



LOSSES IN MANURE 



139 



This fact is presented graphically in the diagram 
which shows tlie distribution of the fertilizing ingred- 
ients in the manure produced from the assumed action. 

DIAGRAM SHOWING DISTRIBUTION OF FERTILIZING 
INGREDIENTS IN MANURE 





[n ^S^§^M$$M$§^$MS^^$^§S§S§^iIb^^^^^^^^ 


rERTILIZINS 
MATERIALS 
IN RATION 




jp.APgg$%^^^^^^^«5^38lb5 


phtJ mum lbs 1 



MANURE 



2952.82 lbs 
3483.50 IbS' 




Value of the dung . 
Value of the urine . 
Value of the bedding 



Total value of manure 



$1,716.88 

1,200.20 

177.12 

$2,094.20 



Plant Food in Liquid Excrement More Available. 

— The above statement does not properly show the 
comparative value of the solid and liquid parts of the 
manure. The plant food in the urine is in a form that 
is soluble in water, and, consequently, much more 
readily available to the plants than that in the solid 
excrement. The solid excrement consists of the undi- 
gested portion of the food, and must undergo thorough 
decay before its fertilizing constituents become avail- 



140 FIRST PRINCIPLES OF SOIL FERTILITY 

able to the plants, so that while something more than 
half of the actual plant food is in the urine, the value 
of the urine is much greater than the dung, owing to 
the better condition of its plant food. The difference 
is due largely to the more available form in which 
the nitrogen exists in the urine. 

That the difference in value of solid and liquid ex- 
crement is not wholly theoretical is shown very nicely 
by a New Jersey experiment. In this experiment two 
plot? were treated with manure, in one case the solid 
excrement only was used, in the other the mixed solid 
and liquid excrement. Each plot received enough of 
the manure to supply exactly the same amount of 
nitrogen, and the other elements were added in excess. 
The results are stated in percentage of gain over a 
check plot that received no manure and are given 
below. 

PERCENTAGE OF GAIN IN YIELD FROM MANURE 

Solid ex- Solid & liquid 
crement only excrement 

First year 15.2 52.7 

SeconcT year 69.7 116.9 

Third year 47.9 80.6 

Average 44.3 83.4 

It will be seen that the yield from the same amount 
of nitrogen was very much larger from the mixed ma- 
nure than from the solid excrement alone. As the 
total amount of nitrogen added was the same in each 
case, the experiment indicates that the nitrogen in the 
liquid excrement was much more readily utilized by the 
plant than was that in the solid excrement. 

Manure is never so valuable as when perfectly fresh. 



LOSSES IN MANURE 



141 



The very best methods of handUng and care, if the 
manure is stored, cannot prevent more or less loss of 
the valuable constituents. For this reason it is advisa- 
ble when possible to apply the manure to the soil a( 




The small stream in the foreground is highly colored by the leachings from the 
pile of manure against the barn. The best part of the manure is being lost 

fast as it is made, a point that will be discussed at some 
length later. 

Losses in Manure From Leaching. — Next to im- 
proper absorption of the urine, the greatest loss in 
manure comes from leaching by rains. As ordinarily 
handled the manure is thrown out each day into the 
open yard to lie for months subject to washing by the 
summer or winter rains. In many cases it is even 
deposited under the eaves of a large barn so as to 
make the washing process more complete. It seems 



142 



FIRST PRINCIPLES OF SOIL FERTILITY 



absurd to go to the trouble of absorbing all the liquid 
excrement by means of bedding, and then to allow it 
to be washed out of the manure by the rains, and yet 
that is what very often occurs. The losses in ma- 
nures due to leaching by rains in the open yard are 
much greater than most people imagine. Many experi- 
ments have been carried on to illustrate these losses. 

At the New Jersey Experiment Station four samples 
of manures were exposed to the weather for varying 
periods and the loss of fertilizing constituents deter- 
mined. The results are summarized in the following 
table : 

LOSSES IN MANURE FROM LEACHING 



Period 


Nitrogen 


Phosphoric acid 


Potash 


Days 


per cent 


per cent 


per cent 


131 


57.0 


G2.0 


72.0 


70 


44.0 


16.0 


28.0 


76 


39.0 


63.0 


56.0 


50 


69.0 


59.0 


72.0 


Average 


51.0 


51.1 


61.1 



It will be seen that the average loss amounted to 
more than half of the value of the manure during 
rather short periods, the longest time being a trifle over 
four months. On many farms the manure is exposed 
to the elements for a much longer period than that 
given in the table. 

In 1890 experiments were conducted at Cornell Uni- 
versity Experimental Station, with manure exposed to 



LOSSES IN MANURE 



143 



the weather for a period of five months (from April 
to September) with the following results: 

Value at beginning Loss Loss 

per ton per ton per cent. 

Horse manure . . . $2.80 $1-74 62.0 

Cow manure .... 2.29 .69 30.0 

Tests at the Central Experimental Farm at Ottawa, 
Canada, with horse manure exposed to the weather 




«^-^ 



Comment 



s unnecessary 



for six months showed a loss of one-third of the nitro- 
gen, one-sixth of the phosphoric acid and one-third of 
the potash, while a corresponding sample that was pro- 
tected from the weather lost only one-fifth of its nitro- 
gen, and none of the phosphoric acid or potash. 

Examples similar to these might be given indefinitely 
from American and European experiments, but it is 



144 FIRST PRINCIPLES OF SOIL FERTILITY 

only necessary here to state that all of these experi- 
ments show great losses in the valuable constituents 
of the manure from exposure to the elements, the de- 
crease in value amounting to from thirty to seventy 
per cent for periods of from three to twelve months. 
These losses vary with the climatic conditions and with 
the quality of the rations. During heavy rains, espe- 




The culvert acrpss the road was built to keep the barnyard dry. The col- 
ored stream which runs through it tells a story of waste of plant food 

cially if occurring in warm weather, the losses will 
be much greater than in dry or cold weather. The 
relative decrease in value is larger for manures pro- 
duced from rations of high nutritive value. In other 
words the more valuable the manure the greater will 
be the percentage of loss from leaching. It is con- 
servative to say that manure exposed to the weather 
for six months loses fully half its value. 

Solid Excrement Loses Value by Leaching. — It is 
not the liquid excrement alone that is washed away by 



LOSSES IN MANURE 



145 



the rains, for the solid excrement contains a certain 
amount of soluble plant food which is removed by 
leaching. In addition to this there are chemical 
changes taking place in the manure which are con- 
verting some of the constituents, which w^ere originally 
insoluble, into forms that are soluble in water, and 
these may be carried away by the rains. Below are 
given the results of experiments at the New Jersey Ex- 
periment Station to determine the losses due to leach- 
ing when the solid excrement alone was considered. 

LOSSES IN SOLID EXCREMENT FROM LEACHING 



Period 


Nitrogen 


Phosphoric acid 


Potash 


Days 


per cent 


per cent 


per cent 


131 


46.0 


72.0 


80.0 


70 


34.0 


27.0 


100 


76 


25.0 


54.0 


48.0 


50 


45.0 


42.0 


42.0 


A verage 


37.6 


51.9 


47.1 



Leaching Removes The Available Nitrogen. — The 

figures given in the above tables representing the per- 
centage of loss of fertilizing constituents from the ma- 
nure do not tell the whole story. The nitrogen in the 
portion removed by leaching is more valuable per 
pound than that which remains, because it is in a form 
more immediately available to the crop. This fact is 
strikingly shown in an experiment at the New Jersey 
Experiment Station in which two plots were treated 



146 FIRST PRINCIPLES OF SOIL FERTILITY 

with quantities of fresh and leached manures which 
would give exactly the same amount of nitrogen. The 
results, stated in percentage of gain over a plot receiv- 
ing no manure, are given below. 

PER CENT GAIN IN YIELD FROM MANURE 

Fresh Leached 

Manure Manure 

First year S^-7 4i-5 

Second year 180.4 96.8 

Third year 117-5 89.6 

Average 11 6.9 76.0 

Open Yard Feeding a Wasteful Practice. — Upon 
a majority of the farms in America, perhaps, the cat- 
tle are fed during the winter in open lots, the manure 
not being hauled away until the following summer or 
fall, if indeed it is removed at all. This method of 
feeding presents ideal conditions for excessive losses 
from leaching, and it is safe to say that more than half 
the fertilizing value of the manure is lost where this 
practice is pursued. In the corn belt of this country 
for instance, large numbers of cattle are fed during the 
winter, and it is not unusual to see a large feeding lot 
covered to a considerable depth with manure which 
is spread out and exposed to the weather in such a 
way that the maximum effects of leaching must take 
place. There is no doubt that considered from the 
fertility point of view alone these farms would be bet- 
ter off if the corn were sold from the farm, and the 
stover all plowed under. 

, Losses Due to Fermentation. — There is another 
source of loss in stored manure that may be quite as 



LOSSES IN MANURE 



147 



wasteful as leaching, i, c, what is known as "hot fer- 
mentation." Manure is very easily decomposed, and 
there is no doubt that decomposition begins almost as 
soon as the excrement is voided by the animal. The 
first evidence of decomposition or fermentation is the 
odor of ammonia that is noticeable in the barn, espe- 
cially in the morning, if the stable has been closed dur- 





Ife " "^^'^^ 




p" ^« 


H 


riHiHli^ll^lHIIHIBL 'i^f-!^^'!V9 



Open lot feeding as extensively practiced in the " corn belt.' More tha half 
the value of the manure is lost by this method of feeding 



ing the night. This is due to rapid decomposition of 
urea, a nitrogeneous substance found in the urine. 
Ammonia contains nitrogen, and when its odor is per- 
ceptible it is a sign that nitrogen is being given ofif 
into the air, and that the manure, therefore, is under- 
going a loss of this valuable constituent. The early 
decomposition of the urea will not be so likely to occur 
if plenty of absorbing material is used. 



148 FIRST PRINCIPLES OF SOIL FERTILITY 

The fermentation of manure is due to different forms 
of bacteria. Some of these germs can exist only in 
the presence of oxygen, and are called "aerobic" bac- 
teria, while others do not require free oxygen, and are 
designated as "anaerobic" bacteria. The aerobic organ- 
isms are responsible for the hot fermentation which is 
the cause of great loss of value in manure. It is well 
known that if manure is thrown loosely into a heap, 
especially if it contains large quantities of horse or 
sheep excrement, it soon becomes very hot and dry and 
oftentimes white or "fire-fanged" as it is popularly 
termed. During this process large losses of nitrogen 
are occurring. Experiments conducted to show the 
loss due to fermentation alone indicate that from thirty 
to eighty per cent of the nitrogen is removed, but that 
the phosphoric acid and potash are not affected. In 
the case of the fire-fanged material in one experiment 
it was found that all of the nitrogen was lost. As 
the value of manure depends for the most part on the 
nitrogen content, it follows that more than half its 
worth may be lost by hot fermentation. 

If the manure heap is so compact that the air cannot 
penetrate it the aerobic bacteria are unable to live, 
and hence hot fermentation is not possible. The pres- 
ence of a large quantity of water also checks this kind 
of decomposition, and for that reason the excrement 
of cows and pigs is not so subject to hot fermentation 
as is that of horses and sheep. Where the manure is 
in a compact mass the fermentations that take place ^re 
due to the anaerobic organisms. These bacteria cause 
decompositions in the manure which convert the inso- 
luble plant food in the excrement into soluble forms, 



LOSSES IN MANURE 



149 



but do so with little loss of the fertilizing constituents 
provided that the heap is protected from leaching rains. 
Always Some Loss in Stored Manures. — Even un- 
der the best of conditions it is impossible entirely to 
eliminate losses in stored manure, although if properly 
preserved the loss may be limited to about ten per cent 
of the nitrogen, and none of the other two constitu- 
ents. This loss, however, is insignificant in comparison 




Waste of manure in a market garden. The manure from the city stables 
was thrown into a loose pile and allowed to undergo hot fermentation and be 
leached by the rains. It should have been carefully piled and protected from 
the weather, 

with the losses which result from not saving the urine, 
from leaching due to rains, or from allowing the ma- 
nure to inidergo hot fermentations, all of which waste 
may be prevented to a great extent as will be explained 
in the next chapter. 



CHAPTER XIV 

PRESERVATION OF MANURE 

Barn Floors Should be Perfectly Tight.— The 
great value of the manure produced on the farm, and 
the losses that may occur in it have been discussed 
at some length. The next point to be considered is the 
best method of caring for manure so as to prevent these 
losses as far as possible. Much that will be said under 
this heading has undoubtedly been already suggested 
to the reader by his perusal of the preceding pages, but 
the subject is of sufficient importance to justify devot- 
ing some space to it, even though repetition becomes 
necessary. 

Attention has been called to the fact that over one- 
half of the value of the manure is in the liquid excre- 
ment, and it is desired to emphasize the statement, 
that the first consideration in caring for manure is to 
have that part of the barn floor upon which the excre- 
ment falls so tight that none of the liquid can drain 
away. The manure trough behind the cattle, especially, 
should be made absolutely tight by the use of pitch, 
cement or some other material that is impervious to 
water. In addition to this care should be used to sup- 
ply litter in quantities large enough to absorb the urine 
so thoroughly that the manure may be removed with- 
out loss from dripping. If the farmer possesses a feed 
cutter he will be well repaid for cutting up all of the 
bedding materials. Straw cut in one inch lengths, for 
150 



PRESERVATION OF MANURE I5I 

instance, will absorb about three times as much urine 
as lone. <;traw. Cutting the bedding not only mcreases 
its abs^'orptive power, but leaves the manure in a condi- 
tion in which it is much more easily handled. Promi- 
nent stockmen have asserted that the greater ease with 
which manure containing short bedding can be re- 
moved, and spread, well repays the cost and trouble 
of cutting all the litter, to say nothing of the saving in 
bedding materials, and the latter is an important item 
on a farm that is stocked to its full capaciy. 

Preservatives May be Used in the Barn.— Most of 
the nitrogen present in the urine exists m the com- 
pound known as urea. This is very readily decom- 
posed by bacteria and changed into a compound of 
ammonia and carbonic acid, and is known as "carbon- 
ate of ammonia." This substance is volatile, and is 
sometimes given off into the air in such quantities as 
to be readily detected by the nose (i. e., by the odor 
or ammonia). This kind of decomposition takes place 
more readily in horse and sheep manures than m that 
from cattle' or swine, as anyone can testify who has 
taken care of these animals when confined m closed 
barns No doubt the reader has gone into the horse 
barn on a winter morning when there was so much 
ammonia in the air that it "made the eyes water. 
When the odor of ammonia is perceptible it means that 
nitrogen is being given oflf from the manure, and the 
loss from this source may be an item of considerable 
importance. This loss may be prevented to some ex- 
tent by the use of gypsum or land-plaster. The addi- 
tion of this substance to a solution of carbonate of 
ammonia brings about a chemical change that converts 



152 FIRST PRINCIPLES OF SOIL FERTILITY 

the ammonia into a compound that is not volatile, and 
hence does not pass off into the air, and at the same 
time the gypsum increases the value of the manure in 
other ways, as will be seen later. In using gypsum 
scatter it on the floor immediately after the barn is 
cleaned, and before the fresh bedding is spread. From 
one-half to one pound per animal each day is the 
amount most commonly used, although more will do 
no harm. It will probably pay better to apply all the 
land-plaster used on the farm with the manure than to 
sow it directly on the ground. 

Kainite, muriate of potash and acid phosphate or 
super-phosphate are often recommended as preserva- 
tives for manure, and to prevent the loss of nitrogen. 
These substances are all said to be injurious to the 
hoofs of animals, and when used should be scattered 
on the floor and carefully covered with bedding. While 
many of the experiments seem to indicate that these 
materials (gypsum included) are efficient in prevent- 
ing loss of nitrogen it must be admitted that there is 
great difference of opinion among authorities as to 
their merits as preservatives. Some experiments have 
indicated that nothing is so efficacious in preventing the 
loss of nitrogen from the manure as a liberal applica- 
tion of dry earth to the stable floor, especially if the 
soil used contains a large amount of humus. In some 
sections of the country it is considered good practice 
to collect and dry out muck soil for use in the stable 
in connection with the bedding. There is no doubt 
that this prevents the loss of ammonia, if properly 
used. Dry earth should not be used in too large quan- 
tities, however, for if sufficient is added to make the 



PRESERVATION OF MANURE 



153 



manure very dry it will cause loss of nitrogen instead 
of preventing it. 

Manure Should be Used When Fresh. — As has 
been said before, manure is never so valuable as when 
perfectly fresh ; for it is impossible even under the best 
system of management to prevent entirely loss of its 
fertilizing ingredients. For this reason the plan of 




The best method to prevent loss in manure is to haul it to the field as fast as 
it is made. This method should be practiced whenever the conditions are 
favorable 



hauling the manure from the barn directly to the field 
is to be recommended whenever there is a field avail- 
able and the weather is suitable. This method of hand- 
ling the manure has many points that commend it to 
the American farmer. In the first place it is the most 
economical of time and labor, as the manure has to be 
handled but once, and, if the barns are conveniently 
constructed, can be removed to the field with little more 
labor than is required to place it in the heap if it is 



154 FIRST PRINCIPLES OF SOIL FERTILITY 

stored. Where the manure is allowed to collect for 
long periods it becomes almost impossible to find the 
time and help necessary to haul it to the field, and the 
temptation to neglect it entirely is almost irresistible. 
Again, almost the total value of the manure is realized 
when it is removed directly to the field and spread over 
the surface of the ground. To be sure the rains falling 
on this manure will leach out the soluble portion, but 
now it will be carried into the soil where it is needed. 
The soluble constituents of the manure are "fixed" by 
the soil so that there is no danger of their being lest. 
If the manure is spread in a thin layer it will not heat, 
so there will be no loss from hot fermentation, and it 
has been demonstrated that where manure simply dries 
out when spread on the ground there is no loss of val- 
uable constituents. 

Stored Manure Should be Protected i^io v. 

Weather. — It is not always possible to remove the ma- 
nure to the field immediately, for there may be none 
ready to receive it or the weather may be such as to 
make it undesirable to haul over the ground. In that 
case it becomes necessary to store the manure for a 
time, and the question is how can this be done with the 
least loss, for it is impossible entirely to prevent loss in 
stored manures. 

In the preceding chapter it was shown that the two 
sources of loss in fertilizing value in the manure after 
it is removed from the barn are leaching, due to rains, 
and hot fermentation. Obviously if the maximum 
value of the manure is to be retained these two injur- 
ious processes must be prevented. The effect of leach- 
ing rains may be overcome in two ways, by providing 



PRESERVATION OF MANURE 



155 



water tight receptacles so that the hquid cannot run 
away, or by keeping the manure under cover so as to 
protect it from the rains. The first of these two meth- 
ods is in general use in some sections of Europe. Pits 
or cisterns of cement or other impervious material are 
built in which to store the manure and in some cases 




One solution of the manure problem. This shed is used to store manure 
only during the periods when it cannot be hauled to the field 

a pump is provided so that the liquid may be pumped 
up, and allowed again to run over the solid portion 
to hasten and control its decay. While this process 
results in the production of manure of excellent quality 
it has little to recommend it to the American farmer, 
for it requires too much time and labor to prepare it, 
and it is not easily applied to the field. Protection of 
the manure from leaching rains by keeping it under 



156 FIRST PRINCIPLES OF SOIL FERTILITY 

cover is more practical and should be in general use, 
for an inexpensive shed or lean-to is all that is needed. 
Where it is possible to provide the shed with a floor 
of some water tight material it is of course desirable 
to do so, as that prevents any danger of loss of liquid 
excrement that might not be properly absorbed by the 
bedding. 

Hot Fermentation Must be Prevented. — The 
whole secret of preventing hot fermentation may be 
summed up in these few words, ''Keep the manure heap 
compact and moist." It has been shown that the heat- 
ing of manure is caused by a class of bacteria which 
require free oxygen for the performance of their func- 
tions. Unless these bacteria are provided with suf- 
ficient air it is impossible for them to live, and conse- 
quently hot fermentation cannot occur. In building the 
manure pile, therefore, great care should be taken to 
have the heap well compacted by tramping or other 
means. Each daily addition to the pile should be 
firmly packed into place, and the sides and top of the 
heap should be made smooth and firm in order to ex- 
clude as much air as possible. If the pile is made in 
this way the aerobic bacteria soon use all the air that 
is enclosed in it, and the manure never becomes very 
hot. The presence of an abundance of moisture tends 
to prevent hot fermentation due first to the cooling 
effect of the moisture itself, and to the fact that the 
moisture prevents the entrance of air. The manure 
heap should be carefully watched, and water added to 
it occasionally if it shows any tendency to become too 
dry. Keeping the pile compact and damp in this way 
will stop the injurious hot fermentation but does not 



TRESERVATION OF MANURE I57 

interfere with the decay due to anaerobic bacteria. The 
latter is beneficial because it decomposes the organic 
matter of the manure in such a way that the plant 
food becomes more available and the manure is greatly 
improved in its mechanical condition. The first step 
in the preservation of manure should be the mixing of 
the dififerent kinds produced on the farm, for in this 
way the rapid fermentation that would take place in 
the drier horse and sheep manure is checked by the 




A convenient method for removing the manure from the barn, but some 
means should be provided to protect the manure from the weather until 
it can be hauled to the field. 



more moist cow and pig excrement. When it is pos- 
sible the manure should be turned occasionally for this 
causes it to decompose more readily and evenly. When 
necessary to store the manure for some time it is a 
good plan to cover the heap with an inch or two of 
earth. This prevents the escape of any ammonia that 
may be formed, as the earth has the power of fixing 
and retaining the ammonia. 



158 FIRST TRINCIPLES OF SOIL FERTILITY 

Covered Barnyards Save Manure. — Roberts and 
other writers recommend the use of covered barnyards 
for the preservation of manure. These are simply 
sheds with good roofs with or without sides and large 
enough to allow the cattle some room in which to 
move about. The bottom is excavated a few inches, 
and made tight by puddling and pounding the clay, or 
by the use of cement. As the manure is removed from 
the barn it should be spread evenly on the floor of the 
covered yard. It will then be tramped into a com- 
pact mass by the moving about of the cattle and kept 
moist by the liquid excrement. The manure produced 
in this way is of excellent quality, can be easily han- 
dled when its removal is necessary and experiments in- 
dicate that the losses are reduced to a minimum. The 
advantages of such a covered yard as a place in which 
the animals will take mild exercise in severe weather 
will be apparent to most farmers. 

A recent circular from the Illinois station presents 
the views of a number of practical dairymen who have 
been in the habit of allowing their cows the freedom 
of a covered barnyard, and using the stable only at 
milking time. The data collected seemed so favorable 
that the plan was put into operation at the station farm. 
Twenty-two cows were cared for in this way in a shed 
30 by 68 feet, having mangers on each side and bull 
pens in two corners, and the results of this trial were 
considered most satisfactory. It is said that the cows 
keep cleaner than when stabled and that the milking 
barn is in a more sanitary condition, consequently, it 
is easier to produce clean milk. Labor is saved, as the 
shed can be bedded more easily and quickly than the 



TRESERVATION OF MANURE 



159 



stalls ; there is little stable cleaning to be done and 
the manure is hauled directly from the shed to the 
field when most convenient, and when there is least 
likelihood of damage to the ground by tramping. AU 
the liquid excrement is absorbed, and if only sufficient 
bedding is used to keep the cows clean they tramp the 




The covered barnyard is probably the very best means of preserving manure 



manure so thoroughly that it does not heat enough to 
make the air impure. 

The plan followed by many farmers of throwing 
horse and cattle manure into a basement room, and 
allowing it to be w^orked over by the hogs is perhaps 
as good a method as could be devised when considered 
from the standpoint of the preservation of manure. 
The working over and tramping of the manure by the 
swine, accompanied by the addition of their own moist 




\ 












1 


"tiD Av-uE-y 








1 






a n ?. J 


















t-a'-^- 


i 














t 


^i r 1 


/ 
















1 




7 









n ;t- 



45 



The covered barnyard, as found on an Ohio dairy farm. When the new dairy 
barn (a section of which is shown in the lower part of the drawing) was built, 
the old barn was retained for use as a covered barnyard. 



PRESERVATION OF MANURE 



l6l 



excrement controls the fermentation so as to prevent 
undue heating, and very Httle fertihzing vahie is lost 
from manure produced in this way if the number of 
pigs is sufficient to work it over thoroughly. 

Deep Stall Manure. — A method of preserving ma- 
nure that is in use in some parts of Europe is what is 
known as the "deep stall method." The stalls in which 






A little expenditure of time and money would convert this into a covered feed- 
ing place where the manure would be fully protected 

the cattle stand are excavated for some depth below 
the general level of the barn floor, and every day the 
manure is spread evenly over the stall, and a liberal 
amount of bedding added. The mixture of excrement 
and bedding is firmly packed by the feet of the cattle 
and is not removed until the end of the winter, the sur- 
face of the manure by this time being above the level 
of the floor. The manure produced in this way is of 



Ib2 FIRST PRINCIPLES OF SOIL FERTILITY 

excellent quality and suffers very little loss in fertiliz- 
ing value. This method will hardly commend itself to 
the farmers of this country for sanitary reasons, espe- 
cially if they are engaged in dairy husbandry. 

How to Care for Exposed Manure. — Occasionally 
it becomes absolutely necessary to store the manure 
when no cover of any kind is at hand. In case it must 
be left in the open, the heap should be made so high 
that even the hardest rains will not soak eniirely 
through it. The sides of the pile should be kept as 
nearly perpendicular as possible, and the top should dip 
slightly toward the center and great care be exercised 
to make the heap compact. Comple'c : "turation of the 
manure does no harm, but any water draining away 
from the heap is certain to carry with it large quanti- 
ties of plant food. 

Composting Manures. — Any method of storing 
manure requires considerable labor, and for that reason 
is to be avoided in general farming whenever it is 
possible to use it in the fresh condition. In market 
gardening, on the other hand, such quantities of ma- 
nure are used that it is necessary to have it thoroughly 
rotted before applying, as otherwise the crop would 
suffer from the heating effect that the large amount of 
raw manure would have on the soil. While the manure 
may be rotted by keeping it in a moist, compact heap 
as described in the previous section, it must be remem- 
bered that the manure commonly used by market gar- 
deners is the horse manure from the city stables. This 
heats so rapidly that special care is necessary to prevent 
hot fermentation, and the pile must be frequently mois- 
tened. Many market gardeners prefer to compost the 



PRESERVATION OF MANURE 163 

manure with earth, peat or muck. This is done by 
making a foundation of about six inches of dirt, and 
on top of this placing alternate layers of manure ai.v. 
soil, moistening the mass as the heap grows. The 
sides and top should be nicely smoothed off and the 
mass covered with a thin layer of earth to prevent loss 
of nitrogen. After about two months the pile should 
be turned over, the materials thoroughly mixed and 
more water added if necessary to keep the compost 
moist. 

A compost in great favor with greenhouse men is 
one made of manure and sod, these materials being 
piled in alternate layers as described above. This gives 
the fibrous compost so desirable for bench and pot 
work. Any of the refuse organic materials of the farm 
or garden may be used in composts. Weeds, refuse 
parts of plants, dead animals, kitchen wastes, etc., may 
be added to the manure-earth mixture, or composted 
separately, for handled in this way they decompose 
rapidly and without oiifensive odors. The presence of 
the earth decreases the loss of ammonia where highly 
nitrogeneous materials are used. 

Some market gardeners throw the horse manure as 
it comes from the city stables into the pig pens to be 
first worked over by the pigs, and then composted with 
the earth, and this plan is no doubt a wise one. 

In using composts a good practice is to add bone 
meal, and one of the potash salts to the heap. In this 
way the plant food in the bone meal is made available 
to the plants, and the compost is made more valuable. 

It occasionally happens that one wishes to produce 
a stock of well rotted manure in a very short time. 



164 FIRST PRINCIPLES OF SOIL FERTILITY 

This can be done by mixing the fresh manure with a 
small quantity of freshly slaked lime. In this way the 
manure is made to decay very rapidly, but as the de- 
composition is probably attended by more loss of nitro- 
gen than usually occurs in composts it is not to be 
recommended for general use. 



CHAPTER XV 

APPLYING MANURE 

Best Used as a Top Dressing. — Nature applies all 
her fertilizers to the surface of the ground. Many 
farmers have come to the conclusion that Nature's 
method is the best, and whenever possible are using 
manure as a top dressing. The tendency is for the 
elements of fertility to pass gradually down into the 
soil, especially the compounds containing nitrogen. 
For this reason it is best to apply the fertilizer to the 
surface so that as the soluble food descends it comes 
into contact with plant roots, and is not carried to such 
a depth as to be beyond their reach. Manure to be 
used in this way must be so fine as not to interfere 
seriously with subsequent tillage of the ground. This 
condition of fineness generally exists if the manure is 
well rotted but even fresh manure may be utilized as 
a top dressing if cut straw or other fine material has 
been used for bedding. It is well to apply the manure 
directly after plowing and to incorporate it thoroughly 
with the soil by use of the harrow or cultivator pre- 
paratory to planting the field. Another reason in favor 
of top dressing over other methods of applying ma- 
nure is that the organic matter added to the surface 
soil in this way acts as a mulch, and tends to prevent 
the evaporation of water from the soil. 

Should be Spread Immediately. — Two general 
methods for the application of manure are in common 

165 



l66 FIRST PRINCIPLES OF SOIL FERTILITY 

use, one is to throw it into heaps where it is allowed 
to remain some time before being spread, the other to 
broadcast it directly from the wagon. The first method 
is objectionable for several reasons. In the first place 
it increases the work necessary to spread the manure 
as it must be handled twice, and it takes no more labor 
to spread it from the wagon than from the heap on 
the ground. When piled in this way it is very often 
allowed to stand for some days at great risk of injur- 
ious fermentations, such as have been described. The 
leachings from these heaps make the spots directly be- 
neath more fertile than the rest of the field, and hence 
produce a rank growth at those places. No doubt the 
reader has often seen a field where he could detect 
every spot upon which the manure heap had been 
placed by the brighter green color and more luxur- 
iant growth of the crop. This uneven growth is unde- 
sirable because in the case of grains it increases the 
danger of lodging in the more fertile spots, and in any 
case it results in unevenness in the maturity of the 
crop. A crop that has a large supply of plant food, 
for instance, has a longer period of growth than one 
with a meager supply, and consequently is later in ma- 
turing. If, therefore, the field is very uneven in fer- 
tility a part of the crop will be ready to harvest some 
time before the rest has matured. If the manure is 
spread directly from the wagon not only is the labor 
lessened but the danger of unevenness in growth is to 
some extent avoided. There is no likelihood of loss 
in the value of the manure when it is spread in a thin 
layer on the ground, as has already been stated. 

Manure spreaders are now being offered for sale of 



APPLYING MANURE 167 

such efficiency that they are hkely to come into general 
use. Some recent experiments seem to indicate that 
manure gives better returns when spread by the ma- 
chine than it does when apphed by hand. Whatever 
method is used to spread the manure it will readily 
be seen that the finer the material the easier it will 




Placing the manure in piles in the field is an objectionable practice. The 
manure should be broadcasted as soon as it is hauled to the field 

be to distribute it evenly. Where very coarse manure 
is used it is sometimes advantageous to supplement 
the spreading from the wagon by the use of a drag 
that will break up the larger lumps, and thus scatter 
it more uniformly. 

Depth to Cover Manure. — Wliere the manure is 
so coarse as to interfere with tillage it becomes neces- 
sary to plow it under, and in this case good judgment 
is necessary to prevent its being covered to too great 
a depth. Especially in clay soils, where the air does 
not readily enter, it is possible to bury the manure so 



l68 FIRST PRINCIPLES OF SOIL FERTILITY 

deeply as to prevent decay. In the case of porous soils 
on the other hand this danger is not so great. In com- 
pact soils the manure should probably never be covered 
to a greater depth than four inches while in sandy 
soils the depth might be much greater. In general 
it may be said that the coarser the manure the greater 
the depth to which it may be buried, while fine and well 
decayed manure on the contrary should remain near 
the surface. In very dry seasons much harm may be 
done to the soil by plowing under large quantities of 
coarse manure as there may not be sufficient moisture 
in the soil to bring about the decomposition of the 
organic matter. The undecayed material may cause 
serious injury to the physical condition of the soil as 
was noted in the discussion of green manure, and the 
suggestion regarding the use of the roller holds good 
in this case. 

Applying to Grass Land. — A practice that is 
highly recommended is to apply the manure, especially 
that of the summer and early fall, to meadow or sod 
land that is to be plowed and planted the following 
spring. In this way of utilizing manure the soluble 
part as it is washed out by the rains is used by the 
growing crop, and thus the losses due to leaching are 
avoided, and as the stubble or sod is turned under the 
entire amount of plant food is in position to be made 
use of by the succeeding crop. The permanent pastures 
should not be neglected in manuring and will well re- 
pay liberal applications. It is well to use the drag 
mentioned above on the pastures so as to spread the 
droppings of the cattle in a uniform manner over the 
surface. When manure is properly applied to pastures 



APPLYING MANURE 169 

or meadows it is beneficial in conserving the moisture 
as well as in supplying plant food, and in inducing a 
longer season of growth. 

Fresh and Rotted Manures Compared. — Few ques- 
tions have been more discussed by the agricultural 
press than the relative merits of fresh and rotted ma- 
nures, and the apparently inconsistent results reported 
by different farmers are probably due more to the var- 




Manure spreader in action. The spreader distributes the manure more evenly 
than can be done by hand, and some experiments indicate that a larger yield 
is obtained from a ton of manure when applied with the machine. 

ious kinds of soil on which the manures were used 
than to any difference in the values of the manures 
themselves. Considered from the standpoint of the 
soil alone, it will be found that on heavy soils contain- 
ing large amounts of clay more benefit will be derived 
from raw manures than from those that are well rotted. 
The fresh manure warms these naturally cold soils, 
makes them more porous, and the fermentations that 
take place during its decay tend to make the soil more 



170 FIRST PRINCIPLES OF SOIL FERTILITY 

mellow and to set free the ''locked up" plant food. 
Rotted manure has the same effect as that which is 
fresh but in a less marked degree. On light or sandy 
soils, on the other hand, those manures that are well 
decomposed will be found more beneficial. Such soils 
are likely to suffer from the heating and drying effect 
of raw manure, and to have their porosity increase to 
an undesirable extent. The manure used on these soils 
if applied in large quantities, should be completely 
decayed, and then it will improve the mechanical con- 
dition of the soil, and materially increase its moisture 
retaining power. 

Raw mr.nure induces rank growth, and for that 
reason i:. ( bjectionable for use on the small grains 
where the product desired is the grain and not the 
\ield of leaf and stem. If manure is used directly on 
these crops it should be thoroughly decomposed. Corn, 
millet and hay crops, on the contrary, are usually ben- 
efited by liberal applications of fresh manure. Corn 
especially is a gross feeder and apparently is not in- 
jured by raw manure even when used in excessive 
quantities. In fact it may be said that when the farmer 
is in doubt as to where to apply the manure he should 
use it on the corn. Manures that are at all fresh are 
injurious to sugar beets and tobacco, in the former 
case producing a large beet that is low in sugar con- 
tent and in the latter a coarse and undesirable leaf. It 
is also a well known fact that raw manure is likely to 
cause wheat to lodge. 

Instead of using manure directly on the grain, beets 
or tobacco it is customary in some parts of the country 
to apply it liberally to corn, and plant the field to the 



APPLYING MANURE 



171 



above mentioned crops the following year. If it is 
used in this way, there is no danger of inducing rank 
growth. 

Amount to Apply. — In a few instances manures are 
wasted by too liberal use. For ordinary farm crops 
it is not customary to use more than eight to ten tons 




Manure spread on the snow. There is no objection to this method of handling 
manure if the ground is fairly level and the snow not too deep. It is certainly 
better than to allow the manure to remain exposed in the barnyard. 



per acre, and on general principles it may be stated 
that somewhat frequent light dressings pay better than 
very large ones given at long intervals. On the other 
hand, the amount of manure produced on the average 
farm is so small when compared with the land to be 
fertilized that it would be utterly impossible to spread 
it over all the farm yearly. For this reason it is a 
good plan to apply the manure to one crop in a rota- 
tion, thus covering only a fraction of the farm each 



172 FIRST PRINCIPLES OF SOIL FERTILITY 

year. The following rotation which is used by a well 
known dairyman is an example that will explain the 
last statement : Corn one year, grain one year, clover 
and timothy two or three years. The manure is ap- 
plied the last year the field is in sod. A second rota- 
tion in common use is as follows: Corn (manured) 
grain, grain, clover. Chemical fertilizers are often 
used on one or both grain crops as well. 



CHAPTER XVI 

BARNYARD MANURE AND THE MAINTE- 
NANCE OF FERTILITY 

Manure as a Crop Producer. — Some difference of 
opinion exists among farmers as to the relative value 
of barnyard manure and commercial fertilizers for 
crop production, but it is worthy of note that those 
who are most diligent in caring for the manure have 
most faith in its worth as a fertilizer. The fact that 
barnyard manure has been used so universally by ag- 
riculturalists for so many centuries is one of the strong- 
est arguments in its favor. That the popular estimate 
of its value is established by scientific experiment is 
well shown by investigations carried on at Rothamsted. 
On certain plots, as has been mentioned, crops have 
been grown continuously with no fertilizer of any 
kind added, on other plots barnyard manure at the 
rate of 14 tons to the acre has been used every year, 
and on still others various combinations of commercial 
fertilizers have been tested. The following table gives 
the yields of barley and wheat from the unmanured 
plots, the plots dressed with barnyard manure, and 
the highest results obtained from the use of any com- 
bination of fertilizing materials. The tests extend over 
40 years, but to shorten the table the results are given 
here in averages for five eight-year periods. (Frac- 
tions have been omitted.) 

173 



174 



FIRST PRINCIPLES OF SOIL FERTILITY 





BARLEY 


WHEAT 




Bushels per A ere 


Bushels per Acre 




t 

S 

1 


II 




s 
1 


II 








^^ 


a^ 


:? 


^- 


a« 


1st 8 years 


24 


44 


48 


16 


34 


36 


2nd 8 years 


18 


52 


51 


13 


35 


39 


3rd 8 years 


14 


49 


45 


12 


35 


36 


4th 8 years 


14 


52 


42 


10 


28 


32 


5th 8 years 


11 


44 


41 


12 


39 


38 


Average (40 years) . 


16 


48 


45 


13 


34 


36 



It will be seen that while both the fertilized plots 
gave much larger yields than the one receiving no 
addition of plant food, there is practically no differ- 
ence between the plots dressed with barnyard manure 
and the best commercial fertilizers. This test is hardly 
fair to the barnyard manure as the quantities of com- 
mercial fertilizers applied were far in excess of any- 
thing used in general practice ; the amount of nitrogen 
added to the wheat, for instance, being equivalent to 
that contained in 8oo pounds of nitrate of soda, which 
would cost practically as much as the wheat would 
bring on the market. In all probability, if these experi- 
ments had been conducted in this country the show- 
ing would have been more favorable to barnyard ma- 
nure. It has been explained that the materials in the 
manure must undergo nitrification before the nitrogen 



BARNYARD MANURE I75 

becomes available to the plants and this process takes 
place so much more rapidly in this country than in 
England that it is easy to believe better returns might 
be obtained from barnyard manure under American 
conditions. 

Lasting Effect of Manure. — Barnyard manure dif- 
fers from other fertilizers in its lasting effect when ap- 
plied to the soil. At Rothamsted, in connection with 
the above experiment, one plot was manured annually 
for 20 years and then received no manure for the next 
20 years. In the accompanying table are given the 
yields of barley in averages for five year periods on 
the plot which was never manured, and the plot that 
had been manured the previous 20 years. The fig- 
ures given for the second plot represent the effect of 
the residual manure, as no fertilizer was added during 
the period covered by the table. 

Eifect of 

Unmanured Residual 

Every year Manure 

First 5 years 13 39 

Second 5 years 14 29 

Third 5 years 14 30 

Fourth 5 years 12 2Z 

Average (20 yrs.) 13.25 30 

The table shows that the effect of the manure was 
perceptible in yield for at least 20 years after the last 
appHcation,, It is more than likely that the more rapid 
rate of nitrification in this country might materially 
shorten the period in which the lasting effect of the 
manure would be observable, and perhaps the influ- 
ence of the residual manure would have disappeared 
in a shorter time than, twenty years, 1 



176 FIRST PRINCIPLES OF SOIL FERTILITY 

Barnyard Manure the Best Fertilizer. — When ev- 
erything is taken into consideration barnyard manure, 
which has been properly cared for, is undoubtedly the 
best substance that the farmer can use as a fertilizer. 
It supplies all the elements of plant food, and while 
these are not all in forms immediately available to the 
plant, a comparison of manure and commercial fer- 
tiHzers during a period of several years is practically 




Corn fertilized with stable manure. This plot gave a yield of 34,800 pounds of 
ensilage per acre. Compare with illustration on opposite page 

always favorable to the former. The value of barn- 
yard manure cannot be estimated from the content of 
nitrogen, phosphoric acid and potash alone, for it is 
probably as valuable on account of its effect on the 
physical condition of the soil as for the plant food 
which it contains. It has no equal among fertilizers 
as a humus former, and the usefulness of humus in 
improving the tilth of the soil and increasing its power 
to hold water was explained in an earlier chapter. 

The use of the animal excrements is also beneficial 
because it increases the desirable fermentations, or 



EARN YARD MANURE 1 77 

bacterial action, in the soil. In fact it seems certain 
that the farmer would be well repaid for applying the 
manure for its indirect effect in improving the condi- 
tion of the soil, even though it contained none of the 
elements of plant food. 

Barnyard manure is also the safest fertilizer to use 
especially by the inexperienced farmer or the one who 
is careless in his methods. There is little danger of 




Corn fertilized with a good complete fertilizer. This plot gave a yield of 29,000 
pounds of ensilage per acre. Compare with illustration on opposite page 

lasting injury to the soil from the use of manure, while 
it is possible to use commercial fertilizers in such a 
way as to make the soil poorer after their use than it 
was before. 

Relation of Manure to Maintenance of Fertility. — 
The discovery of the fact that fully 80 per cent, of the 
fertilizing constituents of the crop can be recovered in 
the manure has thrown a new light on the subject of 
the maintenance of fertility. A number of the most 
prominent authorities on agriculture believe (and the 
belief seems perfectly plausible in view of the facts 



178 FIRST PRINCIPLES OF SOIL FERTILITY 

already discussed) that in a system of strictly animal 
husbandry, where nothing is sold from the farm ex- 
cept animals or animal products, the fertility of the 
land may be maintained indefinitely without the pur- 
chase of fertilizers, provided the manure is properly 
utilized. This assumes, of course, that as nearly as 
possible the full value of the fresh manure is realized 
and that the losses, which have been discussed, are 
avoided. Not only may the fertility be maintained 
in this way but it may actually be increased, as has 
been demonstrated by a number of farmers. 

It has been shown that where the crop is allowed to 
remain on the ground to decay, and become a part of 
the soil, the fertility of the land increases from year to 
year. The fact was also brought out that the soil con- 
tains large quantities of potential plant food, especially 
of the mineral elements and that each year a certain 
portion of this potential food is becoming available. 
The question that suggests itself is whether the food 
rendered available each year is sufficient to make up 
for the 20 per cent lost in feeding the crops to animals. 
There seems to be no reason to doubt that this is so in 
case of the mineral elements even if not true of nitro- 
gen. The 20 per cent loss in feeding falls nearly alto- 
gether on the nitrogen while very little of the phos- 
phoric acid and potash are lost; so that it is easy to 
realize that the supply of these two elements can be 
maintained by the use of the manure and a good sys- 
tem of tillage. The experiments at Rothamsted indi- 
cate that the growth of a crop of clover adds 75 pounds 
or more of nitrogen per acre to the soil, and conse- 
quently this suggests a method of replacing the nitro- 



BARNYARD MANURE I79 

gen lost through feeding. Taking all things into con- 
sideration, it is evident that under the conditions men- 
tioned above it is possible to keep a farm fertile 
indefinitely through the use of the barnyard manure 
produced upon it, supplemented by good tillage and the 
growth of leguminous crops. This statement holds 
true only where no crop is sold. In case the crop is 
sold the entire amount of fertilizing ingredients that 
it contains is removed from the farm. Where the far- 
mer depends for his profit on the sale of animals and 
animal products, however, there is no doubt that the 
fertility can be maintained in the manner described, 
assuming that the farm was in a fair state of fertility 
at the start. Where large amounts of concentrates are 
used, as is often the case in dairy farming, there 
should be an increase in the fertility of the farm if 
the manure is properly handled. 

Effect of Style of Farming on Fertility. — The facts 
brought out by this discussion of the subject of barn- 
yard manure must have made it apparent that the 
losses in fertility are much greater in any system of 
farming where the crops are sold from the farm than 
where some form of animal husbandry is followed, 
especially if no commercial fertilizers are used. To 
bring this point more concretely before the reader the 
following diagram adapted from a Minnesota bulletin 
is given here. 

To obtain the data upon which this diagram is based, 
four farms were assumed each containing i6o acres. 
On the first farm nothing but grain was raised, and 
all sold from the farm. The second was about equally 
divided between grain and stock farming, and the third 



GAIN 


LOSS 


All 
Mixed 
Stock 


Grain Farming 


SmMM^$M$$SS^MM^«$$S$«^ 


w////////////////////m^ 




i42Q0 1 


Farming 






SSMS^IIOO 1 


WM/A 


1000 
1000 




Farming 




1100^$^^^^$^ 


i 


50t 
Dairy 


]60 
Farming 




• 


I200KS;MM 


]85 


y. ...,,,,,,,, 


PHOS. ACID 


-I5t 


;' ' ~ 


NITROGEN 
POTASH 













Diagram showing effect of style of farming on fertility 



BARNYARD MANURE l8l 

and fourth farms were devoted exclusively to stock 
raising and dairying respectively. In the last two 
cases a small amount of the farm produce was ex- 
changed for mill products, which accounts for the slight 
gain in phosphoric acid, but it was assumed that no 
other concentrates or fertilizers were used. The de- 
cidedly smaller loss of nitrogen on the second farm, 
and the actual increase of nitrogen on the stock and 
dairy farms are due to the fixation of nitrogen from 
the growth of clover. The figures represent the num- 
ber of pounds of the fertilizing materials lost or gained 
on the farm in one year. No more striking illustration 
of the effect of the system of farming on the fertility 
of the land could be desired. 



PART IV 
COMMERCIAL FERTILIZERS 




3 - 

3f 



11 






^1 



CHAPTER XVII 

GENERAL CONSIDERATIONS 

Nitrogenous Materials. — It was shown in Part III 
that under a system of animal husbandry it is possible 
to maintain the fertility of the soil by means of the 
barnyard manure used in connection with leguminous 
crops, provided the best methods of tillage, etc., are 
used and all the materials raised are fed on the farm. 
Where a part or all of the crops produced are sold from 
the farm it sooner or later becomes necessary to supply 
plant food derived from outside sources. This is espe- 
cially true in truck farming, where the crops raised are 
such as remove large quantities of plant food. The 
needed fertility is supplied to some extent by the ma- 
nure produced in the city stables, and is best so sup- 
plied when possible, but this source of fertilizing ma- 
terial is obviously inadequate to furnish the required 
amount of plant food. The constantly growing de- 
mand for something that will increase the crop pro- 
duction has given rise to the fertilizer industry which 
is rapidly assuming gigantic proportions. At the pres- 
ent time over $50,000,000 are spent annually in the 
purchase of fertilizers in the United States, and it is 
probably no exaggeration to say that fully half of this 
is money thrown away. This is no argument against 
the use of commercial fertilizers but simply means that 
they should be used with judgment, and not used at 

185 



l86 FIRST PRINCIPLES OF SOIL FERTILITY 

all until actual investigation has shown them to be nec- 
essary. 

Lack of Plant Food Not Sole Cause of Crop Fail- 
ure. — "One must distinguish between lack of plant food 
in the soil and other conditions which prevent good 
crops, for lack of food is not the only cause that makes 
crops suffer. In some soils there is insufficient poros- 
ity, which causes the development of the roots to be 
checked. Lack of moisture, caking of soil, retention 
of stagnant water, deficiency of humus, lime, etc., un- 
favorable weather and other conditions may interfere 
with the healthy growth of plants and thus cause 
diminished crops, even when the plant has within reach 
all the food it needs. Under such circumstances the 
unfavorable conditions must be removed to secure good 
crops, which, according to the demands of special cases 
may be done by irrigating, draining, harrowing, hoe- 
ing, marling, mucking, etc. It may often happen that 
the soil contains an abundance of plant food, most of 
which is still unavailable. Under such circumstances 
an effort should be made to bring this food into an 
available condition as rapidly as the plants can use it, 
and this may be done by an improved system of til- 
lage, together with the application of such indirect 
fertilizers as have the power to make insoluble plant 
food available." — Van Slyke. 

Fertilizers Should Not Take Place of Tillage.— 
Too frequently fertilizers are made to take the place 
of tillage when they should be used to supplement it. 
That is, fertilizers are most likely to produce profitable 
results when conjoined with superior physical condi- 
tions of the soil, and in general terms it may be said 



GENERAL CONSIDERATIONS 



87 



that the man who would obtain the best yield without 
fertilizers of any kind is the one most likely to realize 
a profit from their use. 

'The fact that fertilizers may now be easily secured, 




Thorough preparation of the soil is of prime importance in the growth of crops. 
The upper picture shows buckwheat grown on a soil which was carefully pre- 
pared. The lower cut shows a part of the same field which was hastily and 
poorly prepared, no fertilizer being used in either case. Commercial fertilizers 
should not be expected to take the place of good tillage and cultivation of the 
soil. 

and the ease of application, have encouraged a careless 
use, rather than a thoughtful expenditure of an equiva- 
lent amount of money or energy in the proper prepara- 



l88 FIRST PRINCIPLES OF SOIL FERTILITY 

tion of the soil. Of course it does not follow that no 
returns are secured from plant food applied under un- 
favorable conditions, though full returns cannot be 
secured under such circumstances. Good plant food is 
wasted, and the profit possible to be derived is largely 
reduced." — Voorhees. 

What Are Commercial Fertilizers? — When it was 
first discovered that certain of the elements found in 
the soil are necessary to plant growth it naturally 
occurred to the agricultural investigators that it might 
be possible to renew the fertility of worn out soils by 
supplying these elements artificially. In the first ex- 
periments conducted along this line all the elements 
which the plant derives from the soil were supplied. 
As the investigations progressed it was discovered that 
increased production resulted in most instances from 
the addition of only three of these substances — /. c, 
nitrogen, phosphoric acid and potash. In other words, 
it was determined that except in rare cases all the 
other elements exist in the soil in quantities sufificient 
to supply the needs of the plant, even when the availa- 
ble nitrogen, phosphoric acid and potash are practic- 
ally exhausted. For this reason it is generally con- 
sidered unnecessary to supply any of the elements of 
plant food except the three named above, and these 
substances have come to be known as the "essential 
ingredients of a fertilizer," and the only ones that give 
the fertilizer a commercial value. 

All Fertilizers Made From a Few Basic Materials. 
— From what has been said it will be seen that any 
material that supplies one or more of these "essential 
ingredients" may be used as a commercial fertilizer, 



GENERAL CONSIDERATIONS 189 

provided it could be purchased at a price that would 
make its use profitable. As a matter of fact, the num- 
ber of substances that are available for this purpose 
is somewhat limited, owing to the prohibitive prices 
which the others bring on the market. Many persons 
seem to think that there is something mysterious about 
the manufacture of fertilizers and some of the makers 
encourage this belief by pretending that they have some 
secret process of manufacture that enables them to 
produce a better product than their competitors, and 
far better than the farmer can mix himself. 

The truth is that there are a limited number of 
basic materials from which all the different brands of 
fertilizers are made, and these basic substances are 
articles of commerce and can be purchased by anyone. 
The so-called "complete fertilizers" consist of two or 
more of these substances mixed together in the pro- 
portion to give the required per cent of nitrogen, phos- 
phoric acid, and potash in the finished product. Some 
of these materials are commonly purchased unmixed, 
while others are rarely seen by the farmer except as 
one of the ingredients of a complete fertilizer. Some 
of these basic materials contain only one of the essen- 
tial ingredients of a fertilizer, while others contain two, 
but usually one is in such excess that the substance is 
used chiefiy to furnish that one element. It is possi- 
ble, therefore, to separate the basic fertilizers into three 
classes, viz., 

1. Materials used chiefly as sources of nitrogen. 

2. Materials used chiefly as sources of phosphoric 
acid. 

3. Materials used chiefly as sources of potash. 



190 FIRST PRINCIPLES OF SOIL FERTILITY 

In order to discuss intelligently the subject of com- 
mercial fertilizers it will be necessary to consider 
briefly the substances included in these different classes. 

NITROGENOUS FERTILIZERS 

The larger number of the materials of this class are 
composed of various kinds of refuse animal matter 
from the packing houses, soap and glue factories, etc. 
Only those in common use will be discussed here. 

Dried Blood. — As its name signifies, this is the blood 
from the slaughter house rapidly dried by artificial heat 
and when ready for sale is in the form of a powder. 
Two grades of dried blood are found on the market 
known as the red and the black blood. The red blood 
is more carefully dried, and is not charred as is likely 
to be the case with the black blood, which is more 
rapidly dried. The red blood contains from 13 to 14 
per cent of nitrogen, while the black is much less con- 
stant in composition and contains from 6 to 12 per 
cent. 

Meat Meal, Azotin, Ammonite. — These are synon- 
ymous terms used to designate a meat product derived 
principally from the rendering establishments where 
the different portions of dead animals are utilized. 
When relatively pure it contains from 13 to 14 per cent 
of nitrogen. 

Hoof Meal. — The principal source of this product is 
the glue factory, and it consists of the dried hoof or 
portions thereof ground to a fine powder. It is fairly 
uniform in composition and contains about 12 per cent 
of nitrogen. 



GENERAL CONSIDERATIONS IQI 

Horn Meal is produced at the packing houses and 
in the factories where combs, buttons, etc., are manu- 
factured. The chips and shavings are ground to a fine 
meal and sold as a fertilizer. It is quite uniform in 
composition, containing from lo to 12 per cent of nitro- 
gen, though in a very unavailable form. 

Tankage consists of the dried animal wastes from 
the large slaughtering and rendering establishments. 
It is variable in composition owing to the fact that the 
proportions of the different ingredients of which it is 
composed may vary widely in different samples. As 
commonly made it may include offal, small bones, ten- 
dons, waste flesh, hair, etc. These materials are ren- 
dered for the extraction of the fat, and the residue is 
dried and ground to a meal of more or less fineness. 
Tankage contains phosphoric acid as well as nitrogen 
and the percentage of the two vary. As the nitrogen de- 
creases the phosphoric acid increases, and vice versa. 
The variation of these two ingredients is so great that 
in trade tankage is always sold on the basis of its 
composition. Because it contains very considerable 
amounts of phosphoric acid its commercial value is 
not based wholly on its nitrogen content as is the case 
with dried blood and dried meat. Tankage contains 
from 4 to 9 per cent of nitrogen and from 3 to 12 per 
cent of phosphoric acid. 

Dried Fish or Fish Guano. — Most of the fish ferti- 
lizers are made from menhaden, a fish that is caught 
in large numbers along the Atlantic Coast. The fish 
are steamed and pressed to extract the oil and the 
remaining ''pomace" is dried and ground. This mater- 
ial contains from 8 to 11 per cent of nitrogen and 3 



192 FIRST PRINCIPLES OF SOIL FERTILITY 

to 5 per cent of phosphoric acid. Some of the fish 
fertiHzers consist of the residue of the canning factor- 
ies, but these are not so vakiable as those derived from 
the menhaden. 

Leather Meal consists of the smaller scraps and 
chips from the leather industry ground into a meal 
which is sometimes used in the manufacture of ferti- 
lizers. Leather is fairly rich in nitrogen, but when one 
takes into consideration the fact that the one object 
in making leather is to render it resistant to decay, 
it will be evident that it is not a desirable substance to 
use as a fertilizer. 

Cottonseed Meal and Linseed Meal were formerly 
used as nitrogenous manures, but their value as feeds 
is now so well recognized that they are no longer avail- 
able as fertilizers. 

Peruvian and Other Guanos are composed of the 
accumulated droppings of fish-eating birds, more or 
less mixed with the dead bodies of these birds. The 
most important source of this material was a group 
of islands lying off the coast of Peru, and its high 
value was due to its being produced in a rainless region. 
Guano was formerly abundant, and was so much ap- 
preciated as a fertilizer that many substances in no 
way resembling the true guanos were called by that 
name. At the present time practically no guano of 
good quality is imported, and any product bearing that 
name should be looked upon with suspicion and pur- 
chased only upon analysis. 

Sulphate of Ammonia is a by-product in the manu- 
facture of coal gas, animal charcoal and coke. It re- 
sembles common salt somewhat in appearance, and is 



GENERAL CONSIDERATIONS 193 

the richest in nitrogen of all fertilizing materials, con- 
taining from 20 to 23 per cent. At the present time 
the high price of sulphate interferes with its exten- 
sive use as a fertilizer, although it gives excellent re- 
sults on soils that contain plenty of lime. It should 
never be used on soils deficient in lime nor in connec- 
tion with the ordinary potash fertilizers which contain 
chlorine. 

Nitrate of Soda or Chili Saltpeter is a crystalline 
substance somewhat resembling coarse salt in appear- 
ance and is entirely soluble in water. It all comes from 
large deposits in Chili which supply over one million 
tons of nitrate a year to be used as a fertilizer. Chili 
saltpeter contains from 15 to 16 per cent of nitrogen in 
a form that is immedaitely available to the plant, and 
for this reason it is the most desirable nitrogenous fer- 
tilizer to use where immediate' results are desired. It 
is not fixed by the soil and consequently should be sup- 
plied only as the crop can use it, and never applied 
to the ground when it is bare. As it is so easily washed 
from the soil it is considered best to use it in two or 
three applications instead of applying all at one time. 

Relative Availability of Nitrogenous Fertilizers. — 
The percentage of nitrogen present in the different fer- 
tilizing materials as given in the previous section does 
not properly indicate their relative fertilizing value. 
Mention has repeatedly been made of the fact that the 
plant can make use of the nitrogen only when it is 
present in the soil in the form of nitrates. Nitrate of 
soda is the only fertilizer on the list that contains ni- 
trogen in the nitrate condition, and consequently is the 
only one that adds nitrogen to the soil in a form that is 



194 FIRST PRINCIPLES OF SOIL FERTILITY 

available to the plant without further change. All the 
other materials must undergo the process of nitrifi- 
cation, and have their nitrogen converted into nitrates 
before they can be used by the crop. It must be appar- 
ent, then, that the value of a nitrogenous fertilizer 
depends both upon its content of nitrogen, and the ease 
with which it is nitrified. 

Of the list given above, sulphate of ammonia is the 
most easily converted into nitrates provided the soil is 
abundantly supplied with lime. Next in order comes 
dried blood. So many other uses are being discovered 
for dried blood, however, that the time is probably not 
far distant when it can no longer be used as a ferti- 
lizer. 

The nitrogen in dried fish, tankage, hoof meal and 
bone meal are readily changed by nitrification and rank 
next to blood meal. Horn meal, on the other hand, 
decomposes very slowly, and the nitrification of leather 
is so slow as to make it practically worthless as a fer- 
tilizer. 

Experiments up to date indicate that if nitrate of 
soda is rated at lOO per cent, the availibility of the 
other materials would be as follows: 

Per cent. 

Nitrate of soda loo 

Blood and cottonseed meal 70 

Fish, hoof meal 65 

Bone and tankage 60 

Leather and wool waste 2 to 30 

'Tf for example the increased yield of oats due to 
the application of nitrate of soda is 1,000 pounds, the 



GENERAL CONSIDERATIONS 



195 



yield from blood would be 700 pounds, from hoof meal 
650 pounds and from leather 20 to 300 pounds." 

These statements indicate how little an analysis of 
a fertilizer which gives only the per cent of nitrogen 
or ammonia tells of the real value as a supplier of nit- 
rogen, and show very clearly that to arrive at any con- 
clusion regarding the value of a nitrogenous fertilizer 
one should know the source or condition of the nitrogen 
as well as the per cent. 

Two or three suggestions for the selection of nitro- 




t, ^ Wobout Nitrogen 



Effect of top dressing- grass land with nitrate of soda. The plot on the left 
received no nitrate, the center one half ration, and the one on the right 
a full ration of nitrate. 



gen fertilizers may be deduced from this discussion. 
For those crops which begin their growth early in the 
spring the best results will follow the use of Chili 
saltpeter, as the soil is likely to be poor in nitrates and 
the process of nitrification slow at that time. Such 
crops as have very short periods of growth will re- 
spond best to nitrogen in nitrates. Corn, on the other 
hand, and the other crops which make their growth 
after the season is well advanced can use the slower 
acting fertilizers, as can also those crops which occupy 
the ground permanently. Some agriculturalists prefer 
to use a fertilizer containing nitrogen in three forms 



196 FIRST PRINCIPLES OF SOIL FERTILITY 

for the crops that grow during the greater part of the 
season, a Httle nitrate of soda for immediate use, sul- 
phate of ammonia to supply nitrogen a little later and 
tankage to carry the plant to maturity, all these ma- 
terials being mixed and applied at one time. 

Nitrogen is Expensive. — Nitrogen is the most ex- 
pensive element to supply in commercial fertihzers, 
costing as it does at least three times as much a pound 
as either phosphoric acid or potash. In ordinary or 
''extensive" farming it is seldom profitable to use ni- 
trogenous fertilizers for the nitrogen of the soil can be 
readily maintained by means of the farm manure, and 
a proper use of leguminous crops in the rotation. Mar- 
ket gardening and other forms of intensive farming 
call for a liberal use of fertilizers containing nitrogen. 
A careful study of the materials used to supply nitro- 
gen should be made by those engaged in this style 
of farming for as Wagner says, "The art of manuring 
is dependent upon a rational application of nitrogen.'* 



CHAPTER XVIII 

POTASH AND PHOSPHATE FERTILIZERS 

Potash Sometimes Necessary in a Fertilizer. — It 

has been shown that most soils contain much more 
potash than nitrogen or phosphoric acid. The greater 
part of the potasii in the soil is in very insoluble and 
unavailable forms, and although there are large quan- 
tities present the plant may be able to use so little of 
it that a good crop is impossible, as has been shown 
by the increased yield from the use of potash on clay 
soils that had a high content of this element of fer- 
tility. ''It has been attested that potash is of relatively 
less importance than either nitrogen or phosphoric acid, 
inasmuch as good soils are naturally richer in this ele- 
ment, and because a less amount is removed in general 
farming than of either nitrogen or phosphoric acid, 
as the potash is located to a less extent in the grain 
than in the straw, which is retained on the farm. It 
is, however, a very necessary constituent of fertilizers, 
being absolutely essential for those intended for light, 
sandy soils and for peaty meadow lands, as well as 
for certain potash-consuming crops, as potatoes, to- 
bacco and roots, since these soils are very deficient in 
this element, and the plants mentioned require it in 
larger proportion than do others. In fact it is believed 
by many careful observers, — and the belief has been 
substantiated in large part by experiments already con- 

197 



198 FIRST PRINCIPLES OF SOIL FERTILITY 

ducted, — that the average commercial fertihzer does 
not contain a sufficient amount of this element. It is 
a particularly useful element in the building up of 
worn out soils, because contributing materially to the 
growth of the nitrogen-gathering legumes, an import- 
ant crop for this particular purpose." — Voorhees. 

Wood Ashes at one time was the sole source of 
potash for fertilizing purposes, but at present ashes 
supply but a very small proportion of this element of 
plant food. The potash in wood ashes is one of the 
best forms for use as a fertilizer, but the supply is so 
limited and the price usually demanded so high that 
ashes can no longer be considered as an important 
source of potash. Wood ashes vary greatly in com- 
position, the ash from soft woods containing less pot- 
ash than that from the hard woods ; the content of 
potash ranging from 2 to 8 per cent. 

Potash as found in wood ashes is in a form that is 
very soluble in water so that ashes exposed to the 
weather may have practically all of the potash leached 
out of them. Leached ashes as a rule contain less than 
2 per cent of potash. As it is not possible to distin- 
guish between leached and unleached ashes by mere 
physical examination it is evident that this material 
should be purchased only from guaranteed analysis. 

In addition to potash, ashes contain from 25 to 30 
per cent of lime, and in many cases, doubtless, the bene- 
ficial results obtained from ashes were as much due 
to the lime in them as to the potash. All ashes pro- 
duced on the farm should be carefully preserved and 
utilized, but they can seldom be purchased to advan- 
tage. 



POTASH AND PHOSPHATE FERTILIZERS 199 

Stassfurt Salts. — At the present time practically all 
of the potash used in fertilizing comes from the Stass- 
furt mines in Germany. These mines contain immense 
deposits of potash salts, and are owned by a syndicate 
that controls the price and output of potash the world 
over. A number of different minerals containing vary- 
ing percentages of potash are produced from the mines, 
and many of them are used in Germany. Only three 
or four of these products are in use in this country and 
they are the only ones that will be discussed here. 

Kainite. — This is one of the crude salts which has 
been ground to a powder. It looks somewhat like com- 
mon salt but is darker in color and contains about 12.5 
per cent of potash in the form of sulphate, mixed with 
the sulphate and chloride of magnesia. This substance 
has been used because it is cheaper than the next two 
substances to be mentioned, but even at the lower price 
a ton the actual potash costs more in kainite than in 
the concentrated form. 

Muriate of Potash is manufactured from the crude 
minerals of the mines by concentration, and contains 
about 50 per cent of potash, all of which is combined 
with chlorine in the form known by the chemists as 
potassium chloride. At the present price by the ton 
the muriate supplies potash at a cheaper price a pound 
than any of the other materials. 

Sulphate of Potash is another concentrated product 
of the Stassfurt industry. What is known as high 
grade sulphate contains about 53 per cent of potash 
in the form of sulphate (i. e., combined with sulphuric 
acid). The actual potash in this compound costs a 
trifle more a pound than in the muriate. A lower grade 



200 FIRST PRINCIPLES OF SOIL FERTILITY 

sulphate containing about 26 per cent of potash mixed 
with sulphate of magnesia is sold under the name of 
''double manure salt." Although the price for a ton 
of this material is much less than the muriate or high 
grade sulphate, the cost of the actual potash is a little 
more. 

Comparison of Potash Fertilizers. — All of the ma- 
terials mentioned contain potash in forms that are 
soluble in water so that there is no such marked dif- 
ference in availability as was noted in the case of the 
nitrogen fertilizers, but there is a difference in their 
effect on certain crops and soils due to the substances 
with which the potash is combined. The form in which 
the potash occurs in wood ashes is probably the best 
of all especially for use on light soils, and those which 
are rich in humus or are inclined to be sour; but at 
the prices demanded for wood ashes at the present time 
the potash costs more a pound than in any of the Ger- 
man salts. 

The chlorine in the muriate has been found to be 
injurious to certain crops, among which may be men- 
tioned potatoes, tobacco and sugar beets. Nearly all 
crops are harmed by the muriate if it is apphed in 
large quantities immediately before or after seeding.* 
This injury may be prevented by sowing the muriate 
in the fall as the potash will become fixed by the soil 
and the chlorine will be washed out. When the chlor- 
ine is removed in the soil water it carries with it part 
of the lime so that the soil in fields which are contin- 
uously manured with muriate may become sour through 
removal of the lime. This may be prevented of course 
by occasional applications of lime. The same remarks 



POTASH AND PHOSPHATE FERTILIZERS 20I 

apply to the use of kainite. As the muriate is the 
cheapest form of potash it is the compound that is used 
nearly altogether in mixed commercial fertilizers. 

So far as has been determined, no injurious effect 
results from the use of sulphate of potash, and some 
experiments indicate that larger yields from a pound 
of potash are obtained from the sulphate than from any 
of the other salts. It is the only potash salt that can 
safely be used on potatoes, sugar beets or tobacco. 
Although the potash in the sulphate costs a trifle more 
a pound, it will probably not prove dearer in the long 
run, if the necessity for liming where the muriate is 
used is taken into consideration ; so for continued use 
the sulphate is undoubtedly to be preferred. 

Phosphatic Fertilizers. — Phosphoric acid is present 
in the soil in much smaller quantities than potash, and 
experience shows that it is much more likely to become 
exhausted. In fact there are sections of the country 
where no other fertilizers than those furnishing phos- 
phoric acid are used, while these are bought in large 
quantities. All this class of fertilizers contain their 
phosphoric acid in the form of phosphates i. e., the 
phosphoric acid is combined with some basic substance, 
which is generally lime. The phosphates may be sub- 
divided into two general classes — the natural and the 
manufactured phosphates. 

Natural Phosphates. — There are two general sour- 
ces of phosphates — the bones of dead animals, and 
certain phosphate-containing minerals which will be 
briefly considered. 

Raw Bone Meal is made by grinding raw bones 
to a powder, and the finer it is the more valuable the 



202 FIRST PRINCIPLES OF SOIL FERTILITY 

product. This substance contains about 22 per cent of 
phosphoric acid and 4 per cent of nitrogen. Raw bones 
contain a small quantity of fat as well, and, as this 
prevents rapid decay of the bone, the phosphoric acid 
and nitrogen in the meal are somewhat slowly avail- 
able to the crop. 

Steamed Bone Meal. — Most of the bone meal sold 
at the present time is made from bones previously 
steamed to remove the fat, and a part of the nitrogen 
compounds. The fat is used in making soap and the 
nitrogen in glue and gelatins. Steamed bone contains 
from 28 to 30 per cent of phosphoric acid and about 
i/^ per cent of nitrogen. The steamed bones can be 
ground to a much finer powder, and the removal of the 
fat causes them to decay more rapidly so that they 
must be considered a more valuable source of phos- 
phoric acid than the raw bones. 

Tankage was described under nitrogenous fertiliz- 
ers and is an important source of phosphoric acid in 
the so-called animal fertilizers. When the product 
contains a very large proportion of bone it is some- 
times designated as bone tankage, and may contain 
from 7 to 18 per cent of phosphoric acid. 

Bone Black or Animal Charcoal is made by heating 
bone in air-tight vessels until all the volatile matter is 
driven of¥, and is used in the refineries to purify sugar. 
After it has become spent or useless to the refiner it 
is sold for use as a fertilizer. Bone black contains 
from 32 to 36 per cent of phosphoric acid. 

Mineral Phosphates. — In a number of places rock 
deposits are found that contain varying percentages of 
phosphate of lime. These phosphates, are usually 



POtASH AND PHOSPHATE FERTILIZERS 2O3 

named after the place where they are obtained, as, 
Carolina phosphates, Florida phosphates and Tenne- 
see phosphates. These rocks contain from i8 to 32 
per cent of phosphoric acid, and differ from the bone 
products in that they are purely mineral substances and 
contain no organic matter. Ground into a fine pow- 
der they are sometimes sold under the name of floats, 
but the rock phosphates are used only to a limited ex- 
tent in the -crude condition. 

Superphosphates or Manufactured Phosphates. — 
The phosphoric acid in all of the natural phosphates 




The phosphoric acid found in all fertilizers came originally from bones 
or from phosphate rock. The rock shown in the picture is Tennessee 
phosphate. 

described is combined with lime in a form that is ex- 
tremely insoluble in water. In order to make the phos- 
phate soluble it is sometimes treated with sulphuric 
acid which unites with part of the lime leaving a phos- 
phate which contains only one-third as much lime as 
the natural phosphate and which is soluble in water. 
The lime and sulphuric acid make a compound which 
is the same as that found in gypsum or land-plaster. 
This combination of soluble phosphate and gypsum, 
made by treating the natural phosphates with acid, is 



204 FIRST PRINCIPLES OF SOIL FERTILITY 

called by the various names of superphosphate, soluble 
phosphate, acid phosphate, acidulated rock, etc. For 
its manufacture the rock phosphates are generally em- 
ployed both because they are cheaper and because the 
organic matter in the bones interferes with the use of 
sufficient acid to make all the phosphate soluble. A 
good sample of superphosphate or acidulated rock con- 
tains about 1 6 per cent of phosphoric acid in a form 
that is soluble in water. 

Sometimes when insufficient acid has been used a 
part of the soluble phosphate will change into a form 
intermediate in solubility between the natural phos- 
phate and the acid phosphate, and the phosphate is said 
to have undergone reversion, and the new compound 
is called reverted phosphate. The latter product is 
supposed to be more available to the plant than the 
insoluble or natural phosphate, hence, the soluble and 
reverted phosphoric acid taken together are known as 
the available phosphoric acid. 

In some instances bone meal is treated with a limited 
amount of sulphuric acid and the product is called 
acidulated bone. This substance contains a much 
smaller proportion of its phosphoric acid in the soluble 
form than does the rock superphosphate. When solu- 
ble phosphates are added to the soil they soon combine 
with the mineral matter, and are converted first into 
the reverted phosphate, and finally into the insoluble 
form such as is found naturally in the soil. In this 
way the phosphoric acid is fixed and there is no danger 
of its being lost by leaching. 

Relative Value of Phosphate Fertilizers. — The 
soluble phosphate present in the acidulated goods is 



POTASH AND PHOSPHATE FERTILIZERS 205 

generally considered the most valuable form of phos- 
phoric acid for use as a fertilizer. At first sight it 
seems useless to go to the expense of making the phos- 
phate soluble when it is again rendered insoluble by 
the soil before the plant can make use of it. The real 
object in making it soluble is to aid in its distribution 
in the soil. When an insoluble phosphate is applied it 




elative availability of different phosphates. The labels on the boxes show 
which kind of phosphate was used 

remains where it falls except for the slight distribution 
it receives by cultivation. In the case of the soluble 
phosphate, on the other hand, the phosphate dissolves 
in the soil water and is widely distributed before it 
becomes fixed by the soil. In the former case the roots 
must go to the phosphate while in the latter the phos- 
phate is carried to the roots. It follows from what 
has been said that after the soluble phosphate is dis- 
tributed throughout the soil the individual particles 
must be very much smaller than is the case with the 



2o6 



FIRST PRINCirLES OF SUIL FERTlLFrY 



insoluble phosphate ; the importance of fineness of divi- 
sion was clearly shown in the discussion of tillage. 

There are some soils upon which the superphosphates 
cannot be used without injury, usually those that are 
deficient in lime, the superphosphate in such cases hav- 
ing a tendency to make them acid. Indeed, it is even 



asserted that soils containing an abundance of 



lime m 




Relative value of phosphate fertilizers. All pots received the same amounts of 
plant food, but 7 received its phosphoric acid from acid phosphate, 5 from 
bone meal and 3 from ground phosphate rock or "floats." 



the begiiming may be made acid by the continued use 
of superphosphate if no lime is added. 

When the natural phosphates alone are considered 
there is no doubt that the preference should be given 
to those derived from bones. The organic matter 
present in the bones decays when it is incorporated 
with the soil, and this process doubtless causes the 
phosphate to become more readily available to the 
plant, while the rock phosphate on the contrary is very 



POTASH AND PHOSPHATE FERTILIZERS 207 

slowly decomposed. The degree of fineness to which 
bone meal or mineral phosphate is ground is of prime 
importance. Very fine bone meal is much more avail- 
able than that which is coarser and is always rated at 
a higher price a ton. 

Using Floats With Manure. — The use of floats, or 
finely ground phosphate rock, has not met with general 
favor, and it probably does not give good results when 
used alone. Some of the earlier experiments indicate 
that it has practically no value as a source of phos- 
phoric acid for the plant. Recent investigations at the 
Ohio and Illinois Experiment Stations show that when 
floats is added to farm manure it has a very high fer- 
tilizing value ; in fact the increased crop production in 
Ohio due to adding the ground rock phosphate to 
the stall manure was nearly as large as that obtained 
from the addition of superphosphate. The acid sub- 
stances produced during the decay of the manure ap- 
parently make the phosphoric acid in the rock more 
available, and it would seem from these experiments 
that the comparatively inexpensive floats might, par- 
tially at least, replace superphosphate if used in con- 
nection wath the manure. Other experiments have 
demonstrated that good results can be obtained from 
the use of ground rock phosphate, when plowed under 
with a green manure crop like clover, but that it is of 
very little value if used on a soil low in organic mat- 
ter. In a plot experiment at the Massachusetts Experi- 
ment Station two ''equal money's worth" of ground 
Carolina rock and superphosphate w^ere compared. In 
this case the superphosphate proved superior at first, 
but within a few years the plot to which rock phos- 



208 FIRST PRINCIPLES OF SOIL FERTILITY 

phate was added gave higher yields. It would seem, 
on the whole, that the use of floats with manure is 
worthy of a trial by anyone needing a phosphate fer- 
tilizer. Ohio Bulletin 134, recommends that the ground 
rock be used '*as an absorbent in the stable, thus secur- 
ing an intimate mixture with the manure in its fresh 
condition." 



CHAPTER XIX 



MIXED FERTILIZERS 



Complete Fertilizers. — Mention was made of the 
fact that the basic materials described in the foregoing 
sections contain only one, or at most two, of the essen- 
tial elements of fertility. By far the larger part of 
the commercial fertilizers used by the farmers in this 
country are purchased in the form known as complete 
fertilizers. A complete fertilizer, in the sense in which 
the word is used in trade, is one that contains nitro- 
gen, phosphoric acid and potash, in proportions that 
are supposed to be suited to the requirements of farm 
practice. Practically all of these fertilizers are made 
by mixing tw^o or more of the basic materials hereto- 
fore described, the different ingredients being so com- 
bined as to give the desired percentage of nitrogen, 
phosphoric acid and potash. In case the basic ma- 
terials alone yield a product that is richer in the essen- 
tial ingredients than is desired by the manufacturer, 
sufficient gypsum, dry earth, peat or other inert matter 
is added to bring the percentage of these ingredients 
down to the desired point. Materials added in this way 
are known as fillers.'*^ These fertilizers are indiscrim- 

* There is a mistaken notion which is quite prevalent that anything 
contained in a fertilizer except nitrogen, phosphoric acid and potash is 
a filler. As a matter of fact it is impossible to make any rational com- 
bination of the basic materials which will contain more than one-third 
of its total weight of the three "essential ingredients," for even in the 

209 



2IO FIRST PRINCIPLES OF SOIL FERTILITY 

inately recommended for general use and all sorts of 
startling claims are made for them by the various man- 
ufacturers. They are offered as universal fertilizers, 
irrespective of the well known fact that soils differ 
widely in their characteristics and that the crops vary 
in their food requirements. To be sure, a fertilizer of 
this kind if sufficiently rich in nitrogen, phosphoric acid 
and potash might be made to produce a large yield 
on any kind of soil if used in quantities, but such a use 
of a fertilizer would result in adding some of the ele- 
ments at least in amounts far in excess of the need of 
the crop. The profits of ordinary farming are not 
sufficient to warrant the application of any of the ele- 
ments of plant food in larger quantities than is re- 
quired by the plant. An economical use demands that 
fertilizers be adapted to the soil, and to the crop to, 
be raised, and this end can rarely be attained by the 
use of complete fertilizers. A little thought on the part 
of the farmer will convince him that the use of these 
general fertilizers is irrational, and that to obtain the 
best results he must adopt some system of fertiliza- 
tion especially adapted to his particular conditions. 

Special Fertilizers. — A large number of so-called 
special fertilizers now offered by the manufacturers 
are supposed to be adapted to the particular needs of 
a special crop or class of crops. Each fertilizer usually 
bears the name of the particular crop for which it is 
designed. Such fertilizers are offered for all of the 

highest grade materials the nitrogen, phosphoric acid and potash are 
combined with other substances. A filler, properly speaking, is a 
substance added for the express purpose of diluting the fertilizer and 
usually contains no plant food whatever. No filler is used in the 
highest grade mixed goods. 



MIXED FERTILIZERS 211 

prominent crops. There are found on the market, corn 
specials, tobacco specials, potato specials, trucker's fav- 
orite, etc., etc., many manufacturers offering a number 
of such products. 

If such fertilizers were compounded with any regard 
to the requirements of the particular crop for which 
they were advocated their use would be a distinct ad- 
vance over the use of the general co.mplete fertilizers. 
Unfortunately their chief claim is in their attractive 
names, and their composition is rarely in accord with 
what scientific investigation has shown to be necessary 
for the crop. That these mixtures are not based on 
any scientific knowledge of the needs of the plant is 
shown by the fact that the specials oft'ered for the 
same crop by the different manufacturers vary as 
widely in composition as do the fertilizers offered for 
different classes of crops. Yet these several makers 
are all claiming to have the best fertilizer for that par- 
ticular crop. A recent bulletm giving the guaranteed 
analysis of the fertilizers offered for sale in the State 
of Ohio contains some data on this subject, and as the 
conditions in other states are undoubtedly similar, it 
may be interesting to call attention to a few facts 
brought out by an examination of this bulletin. Forty- 
four of the fertilizers on the list are especially recom- 
mended for potatoes under such names as, Potato 
Grower, Potato Special, Potato and Tobacco Special, 
etc. These specials are widely variable in composition 
as is shown by the following table which gives the 
guaranteed analysis of seven of them, selected to show 
the variation in per cent of ammonia, phosphoric acid 
and potash. 



212 FIRST PRINCIPLES OF SOIL FERTILITY 

Ammonia Phos. Acid Potash 

Number percent, percent. percent. 

I 2 10 4 

2 I 10 4 

3 3 10 6 

4 I 6 10 

5 .1 8 6 

6 2 7 6 

7 . . . • I 12 6 

In view of such a lack of uniformity in composi- 
tion, the farmer who places his dependence on these 
special fertilizers, must be at a loss to know which one 
to select. The general experience of farmers in the 
Eastern states where fertilizers have long been used on 
potatoes, indicates that the best combination for this 
crop is one that contains potash in excess of the phos- 
phoric acid. Voorhees recommends a mixture contain^ 
ing nitrogen 3 to 4 per cent, phosphoric acid 6 to 8 
per cent., and potash 8 to 10 per cent. In spite of this 
fact only four out of the forty-four specials mentioned 
above contain potash in amounts exceeding the i)hos- 
phoric acid. And lastly, two-thirds of the special 
potato fertilizers contained potash in the form of 
muriate. The authorities are practically all agreed 
that the muriate is injurious to the potato, and that all 
the potash used on this crop should come from the 
sulphate, and yet only one-third of these fertilizers 
under discussion contained potash in this form. Sim- 
ilar discrepancies are found in the special fertilizers 
offered for crops other than the potato. These facts 
are sufficient to convince one that little dependence can 
be placed upon the name under which a fertilizer is 



MIXED FERTILIZERS 2I3 

sold. Even were this idea of special fertilizers for each 
crop carried out consistently it does not take into ac- 
count the fact that soils are very different in their 
fertilizer requirements for the same crop, and that a 
given crop may fail in one place for lack of nitrogen 
while the failure in another case may result from an 
insufficient supply of phosphoric acid or potash. These 
special fertilizers militate against progressive farming, 
for the farmer who uses these mixtures is too apt to 
place his reliance upon them instead of intelligently 
studying the needs of his own soil and crops, without 
which study no use of fertilizers will long be success- 
ful. 

High and Low Grade Fertilizers. — As the basic 
materials show great variation in the amounts of fer- 
tilizing ingredients they contain, it will readily be seen 
that products made by mixing these materials will con- 
tain very different percentages of nitrogen, phosphoric 
acid and potash. If dried blood, steamed bone meal 
and muriate of potash were used, for instance, the 
fertilizer would have a high content of the three essen- 
tial elements, while if low grade tankage and wood 
ashes or kainite were employed the product would have 
a much lower percentage of the three named substan- 
ces. The use of a filler as well makes it possible to 
have an almost endless variety in the composition of 
fertilizers, and hundreds of different brands are offered 
in the market. It is customary to designate those hav- 
ing large amounts of plant food as high grade goods 
and those low in plant food as low grade. While no 
hard and fast line can be drawn between high and low 
grade goods it may be said that any complete ferti- 



214 FIRST PRINCIPLES OF SOIL FERTILITY 

lizer that contains less than two per cent of nitrogen 
should be considered low grade. 

The terms, high grade and low grade, are used by 
some writers to distinguish the condition of the plant 
food in the fertilizer and not the amount. Leather 
meal, therefore, would be classed as low grade because 
the nitrogen in it is in an unavailable form although 
the amount is relatively high. It may be stated as a 
general rule that the fertilizers containing the largest 
amounts of plant food usually have it in the most desir- 
able condition, while the materials containing the 
toughest forms of plant food are used to make the 
cheaper fertilizers, 

Expensiveness of Cheap Fertilizers. — A large part 
of the commercial fertilizers used by the farmers at the 
present time is purchased in the form of cheap mixed 
or complete fertilizers. The low price is attractive, 
and, to many people a fertilizer is a fertilizer, irrespec- 
tive of its composition. Consequently this class of 
goods is sold more readily than those of a higher price, 
although the plant food in the cheap fertilizers actually 
costs more a pound. This fact is very clearly set forth 
in a recent bulletin of the New York Experiment Sta- 
tion from which the table following has been adapted. 
The analyses of all the fertilizers sold in the State 
have been compiled, along with the retail prices, and 
from these data the price a pound paid for nitrogen, 
phosphoric acid and potash in the different grades of 
goods has been calculated. 

The fertilizers have been divided into four classes 
as follows : ( I ) Low grade having a commercial valua- 
tion of less than $i6 a ton ; (2) medium grade from $16 



MIXED FERTILIZERS 



215 



to $20; (3) medium high grade, from $20 to $25; 
(4) high grade over $25. For the sake of comparison 
a few of the basic materials are included in the table. 



AVERAGE COST OF ONE POUND OF PLANT FOOD TO CON- 



SUMERS 








Nitro- 


Phos. 


Pot- 




gen 


Acid 


ash 




cents 


cents 


cents 


Low grade complete fertilizers . 


. . 26.3 


8.0 


6.8 


Medium grade complete fertilizers 


. 23.2 


7.0 


6.0 


Medium high grade complete fertilizers 21.0 


6.4 


5.4 


High grade complete fertilizers 


. 19.6 


6.0 


5.0 


Dried blood 


. 18.5 


... 


... 


Bone meal 


. 14.9 


3.96 




Nitrate of Soda 


• 13-9 




... 


Acid phosphate 





5-1 


... 


Sulphate of potash .... 






5.0 


Muriate of potash .... 







46 



It will be seen that the price a pound of plant food 
is very much less in the high grade goods than in 
the low grade. If the fertilizer is to be shipped any 
distance there is another point in favor of the high 
grade goods for it costs no more for freight on a 
ton of a high priced fertilizer than on a ton of a low 
priced one, while the former may contain twice as 
much plant food as the latter. 

Home Mixed Fertilizers. — The above table not only 
shows that plant food is cheaper in high grade ferti- 
lizers than in low grade, but also that the essential 
elements can be purchased more cheaply in the basic 
materials than in any mixed fertilizer. This is due 
to the fact that the manufacturer must be paid for 



2l6 FIRST PRINCIPLES OF SOIL FERTILITY 

mixing, bagging, etc. Voorhees has shown by careful 
investigation that the average charges of the manu- 
facturer for this work amount to $8.50 a ton. In other 
words, the plant food in one ton of a mixed fertilizer 
can be purchased by the farmer for from $6 to $10 
less in unmixed materials. This fact suggests the 
thought that it might be possible for the farmer to buy 
the basic materials and prepare his own mixed ferti- 
lizers. The matter of home mixtures has been care- 
fully studied by a number of experiment stations and 
it has been shown conclusively that the materials can 




Potatoes grown without fertilizers. The small pile on the left only is marketable 

be evenly mixed on the farm, that the mechanical con- 
dition is good, and that the results obtained from their 
use are entirely satisfactory. It would not be advisa- 
ble to try to make the superphosphate on the farm, but 
the plain rock-superphosphate can be purchased to mix 
with the other materials. There are some obvious ad- 
vantages other than cheapness in home mixing over 
the purchase of mixed fertilizers. The usual analysis 
of a mixed fertilizer gives no clue as to the condition 
or source of the nitrogen, and it is difficult to deter- 
mine its availability, while in the home made mixture 
the condition of the nitrogen should always be known. 



MIXED FERTILIZERS 21/ 

Home mixing permits the uniting of the different ele- 
ments in the proportions which have been found to meet 
the requirements of the crop best and the soil on 
which it is to be raised, something that is not easily 
managed with factory rtijxed fertilizers. By buying 
the basic materials separately it is possible to apply the 
different elements at different times, a point that is 
sometimes of great advantage in feeding a crop, espe- 
cially if it is one that needs large quantities of nitro- 






fc •,^, H<p* K. '^ A, --«^,'5#-^ • -^j, f»\i- 






< 






■:.^M^: 




Potatoes with complete fertilizer. Marketable potatoes on the left. Com- 
pare with cut on opposite page. Fertilizers increase not merely the yieli 
but the quality as well, 

gen. In fact the only advantage that can consistently 
be claimed for the mixed goods is that they are more 
generally distributed in the market than the basic ma- 
terials and can, therefore, be more easily purchased in 
such amounts and at such times as are convenient. 

The conditions existing upon the majority of farms, 
are such that an elaborate arrangement, even for mix- 
ing small quantities at a time, will not be brought into 
use, and a tight barn floor and square pointed shovel 
will be the only requisites at disposal. Under such 



2l8 



FIRST PRINCIPLES OF SOIL FERTILITY 



circumstances after weighing out the quantities to be 
mixed they should be spread upon the floor in layers 
one upon the other. Then beginning at one side and 
working across, the whole should be shoveled over ; 
this may be leveled somewhat and the operation re- 




An outfit for the home mixing of fertilizers. The grinding machine is neces- 
sary. If the materials are lumpy, but if they are fine the screen and shovel 
alone are needed. 



peated until the mixing is satisfactory. In addition to 
the shovel and the barn floor a large screen such as 
is used in screening gravel or coal ashes, may be em- 
ployed with decided advantage; the material at the 
first can be thrown upon the screen and by this means 
lumps may be separted and more easily broken up and 
the thoroughness of the mixing will be increased. 



CHAPTER XX 

USING COMMERCIAL FERTILIZERS 

Fertilizers are used primarily in order to obtain an 
increased profit through the larger yield of the crop 
to which they are applied. From what has already 
been said, it must be evident that the fertilizer to be 
used depends on the soil and the particular crop to be 
raised. An economical and profitable use of commer- 
cial fertilizers calls for much more thought and study 
than the farmer has been accustomed to devote to the 
subject, for until he has a fair knowledge of the nature 
of his soil and the requirements of the crop he desires 
to produce he is not prepared to use good judgment in 
the selection of his fertilizing materials. Every far- 
mer should conduct certain experiments on his own 
soil to ascertain what substances give the best results, 
but the majority of them are loath to undertake these 
experiments and prefer to follow some more general 
system (or lack of system) in the use of fertilizers. 
Commercial fertilizers have been on the market for a 
sufficient length of time to have been widely employed 
and as might have been surmised there have been 
developed a number of dififerent plans or systems for 
their use which vary somewhat in the principles on 
which they are based, and which will be discussed 
briefly. 

Ville System. — "The one which has perhaps re- 
ceived the most attention, doubtless largely because 

219 



220 FIRST PRINCIPLES OF SOIL FERTILITY 

one of the first presented, and in a very attractive man- 
ner, is the system advocated by the celebrated French 
scientist, George Ville. This system, while not to be 
depended upon absolutely, suggests lines of practice 
which, under proper restrictions, may be of very great 
service. In brief, this method assumes that plants may 
be, so far as their fertilization is concerned, divided 
into three distinct groups. One group is specifically 
benefited by nitrogenous fertilization, the second by 
phosphatic and the third by potassic. That is in each 
class or group, one element more than any other rules 
or dominates the growth of that group, and hence each 
particular element should be applied in excess to the 
class of plants for which it is a dominant. In this 
system it is asserted that nitrogen is the dominant 
ingredient for wheat, rye, oats, barley, meadow grass 
and beet crops. Phosphoric acid is the dominant fer- 
tilizer ingredient for turnips, Swedes, Indian corn 
(maize), sorghum and sugar cane; and potash is the 
dominant or ruling element for peas, beans, clover, 
vetches, flax and potatoes. It must not be understood 
that this system advocates only single elements, for 
the others are quite as important up to a certain point, 
beyond which they do not exercise a controlling in- 
fluence in the manures for the crops of the three 
classes. This special or dominating element is used 
in greater proportion than the others, and if soils are 
in a high state of cultivation, or have been manured 
with natural products, as stable manure, they may be 
used singly to force a maximum growth of the crop. 
Thus, a specific fertilization is arranged for the var- 
ious rotations, the crop receiving that which is the 



USING COMMERCIAL FERTILIZERS 221 

most useful. There is no doubt that there is a good 
scientific basis for this system, and that it will work 
well, particularly where there is a reasonable abun- 
dance of all the plant food constituents, and where the 
mechanical and physical qualities of soil are good, 
though its best use is in "intensive" systems of practice. 
It cannot be depended upon to give good results where 
the land is naturally poor, or run down, and where the 
physical character also needs improvement." 

Wagner System. — ''Another system which has been 
urged, notably by German scientists, is based upon the 
fact that the mineral constituents, phosphoric acid and 
potash, form fixed compounds in the soil, and are, 
therefore, not likely to be leached out, provided the 
land is continuously cropped. They remain in the soil 
until used by growing plants, while the nitrogen, on 
the other hand, since it forms no fixed compounds and 
is perfectly soluble when in a form useful to plants, is 
liable to loss from leaching. Furthennore, the min- 
eral elements are relatively cheap, while the nitrogen 
is relatively expensive, and the economical use of this 
expensive element, nitrogen, is dependent to a large 
degree upon the abundance of the mineral elements 
in the soil. It is, therefore, advocated that for all crops 
and for all soils that are in a good state of cultivation, 
a reasonable excess of phosphoric acid and potash shall 
be applied, sufficient to more than satisfy the maxi- 
mum needs of any crop, and that the nitrogen be ap- 
plied in active forms, as nitrate of soda, and in such 
quantities and at such times as will insure the minimum 
loss of the element and the maximum development of 
the plant. The supply of the mineral elements may 



222 FIRST PRINCIPLES OF SOIL FERTILITY 

be drawn from the cheaper materials, as ground bone, 
tankage, ground phosphates and iron phosphates, as 
their tendency is to improve in character ; potash may 
come from the crude salts. Nitrogen should be applied 
as nitrate of soda, because in this form it is imme- 
diately useful, and thus may be applied in fractional 
amounts, and at such times as best meet the needs of 
the plant at its different stages of growth, with a 
reasonable certainty of a maximum use by the plants. 
Thus no unknown conditions of availability are in- 
volved, and wdien the nitrogen is so applied, the dan- 
ger of loss by leaching, which would exist if it were 
all applied at one time is obviated." — Voorhees. 

System Based on the Analysis of Plant. — Still an- 
other system is based on the food requirements of the 
plant, as shown by the analysis of the plant itself. The 
amount of plant food removed from each acre of 
ground is calculated from the analysis of the plant and 
a corresponding amount is returned to the soil. Dif- 
ferent formulas are, therefore, recommended for each 
crop, and in these the nitrogen, phosphoric acid and 
potash are combined in the proportions in which they 
are found in the plant. Experience shows that it is 
necessary to add amounts of these fertilizers to the soil 
that will supply more plant food than is removed by 
the crop if the maximum results are desired. This 
system may result in a large yield but cannot be con- 
sidered an economical method of feeding the plant, as 
one or more of the elements is likely to be applied in 
excess of the requirements of the crop. It does not 
take into consideration, for instance, the fact that a 
plant which contains a large amount of one element 



USING COMMERCIAL FERTILIZERS 223 

of plant food may possess unusual power of procur- 
ing that element from the soil. The principle under- 
lying this system of course, is the idea that to maintain 
the fertility of the soil unimpaired an amount of plant 
food equivalent to that removed by the crop must be 
returned to the land. To this extent the system is sim- 
ilar to the use of barnyard manure but is not so effec- 
tive. 

Fertilizers Applied to Money Crops. — Another 
system used in ordinary or extensive farming is to 
apply all the fertilizer to the money crop in a rotation. 
This method is used especiaFly where only one crop in 
a rotation is sold, the others being fed on the farm. 
A liberal supply of food is used to give the maximum 
yield which the climate and season will permit. The 
amount of food applied is in excess of the require- 
ments of the crop and the residue is depended upon 
to help nourish the succeeding crops, or at least the 
one immediately succeeding the money crop. This 
system has some valuable features and is probably the 
one most in use in this country at the present time. 

Irrational System. — Too frequently fertilizers are 
used by what certain writers call the hit or miss 
system. No special thought is given to the require- 
ments of the crop or the composition of the fertilizer, 
but if the farmer feels that he can afford it and the 
agent is a glib talker, the sale is made. If the buyer 
happens to hit the food requirements of his crop a 
profit is secured and he is correspondingly happy, 
while if he makes a miss he feels assured that there 
is no value in commercial fertilizers. 



224 FIRST PRINCIPLES OF SOIL FERTILITY 

Weak Points in These Systems. — All of these sys- 
tems, with the exception of the last one mentioned, 
have their good features and have proved remunera- 
tive in the hands of many of their advocates. They 
all have, however, one weak point in common, i. c, 
they do not take into consideration the fact that dif- 
ferent soils contain varying amounts and proportions 
of plant food, and that while a certain soil may be 
lacking in potash, for instance, it may contain amounts 
of nitrogen and phosphoric acid sufficient for a maxi- 
mum yield. Such a soil would obviously be benefited 
by an application of potash, while nitrogen and phos- 
phoric acid would produce no effect. Experiments 
have shown that on ordinary soils it seldom happens 
that all three of the elements of fertility are required 
at one time. Unfortunately there is no easy way of 
determining accurately the fertilizer requirements of a 
soil for a particular crop. Van Slyke has formulated 
the following general rules which may be of value 
where no accurate data are at hand. 

Growing Crop Should Be Studied. — 'Tt is impos- 
sible to give any fixed rules which will cover all cases 
and enable a farmer to tell without any experiment on 
his part what food constituents his soil lacks. In a 
general way, the crops themselves may give some val- 
uable suggestions. 

1. As a rule, lack of nitrogen is indicated, when 
plants are pale-green, or when there is small growth 
of leaf or stalk, other conditions being favorable. 

2. A bright, deep-green color, with a vigorous 
growth of leaf or stalk, is, in case of most crops, a 
sign that nitrogen is not lacking, but does not neces- 



USING COMMERCIAL FERTILIZERS 225 

sarily indicate that more nitrogen could not be used 
to advantage. 

3. An excessive growth of leaf or stalk, accompanied 
by an imperfect bud, flower, and fruit development, 
indicates too much nitrogen for the potash and phos- 
phoric acid present. 

4. When such crops as corn, cabbage, grass, pota- 
toes, etc., have a luxuriant, healthful growth, an abun- 
dance of potash in the soil is indicated ; also, when 
fleshy fruits of fine flavor and texture can be success- 
fully grown. 

5. When a soil produces good, early maturing crops 
of grain, with plump and heavy kernels, phosphoric 
acid will not generally be found deficient in the soil. 

Such general indications may often be helpful, and 
crops should be studied carefully with these facts in 
mind." 

Field Experiments to Determine Fertilizers 
Needed. — All the methods so far suggested for deter- 
mining the kind of fertiUzer to be used are open to 
objection because of the large element of uncertainty 
involved. It has been repeatedly pointed out that indi- 
vidual fields differ in their power to supply the crop 
wath plant food even when the respective soils are 
very similar in appearance. None of the plans de- 
scribed provide for any control experiment to show 
whether the use of the fertilizer has been really profit- 
able. The only rational way of ascertaining the proper 
fertilizing material to use on a given field is to compel 
the soil itself to answer the question. This can be done 
by a set of simple and easily conducted field experi- 
ments which every one should conduct on his own 



22^ FIRST PRINCIPLES OF SOIL FERTILITY 

farm. These experiments consist simply in dividing a 
small portion of the field into small plots on each of 
which a different kind of fertilizer is used, the yield 
being compared with check plots to which no ferti- 
lizing material has been added. The different crops 
vary in their power to extract plant food from the 
soil, consequently, these experiments should be con- 
ducted with the particular crop or crops on which the 
fertilizer is to be used. 

Conducting The Experiment. — The first import- 
ant consideration in an experiment of this kind is the 
selection of the location for the plots. The spot 
selected should represent as nearly as possible the 
average condition of the entire field. The soil should 
be uniform in quality over the entire area devoted to 
the experiment so that one may feel sure that any 
difference in yield from the several plots is not due 
to variation in the composition of the soil. Plots i rod 
wide and 8 rods long (containing one-twentieth acre) 
will be found a convenient size for the purpose, but any 
other size could be used. The simplest experiment 
which will give any reliable information calls for a 
row of at least seven such plots, with a space of at 
least 3 feet between each plot. The ground is first 
plowed and harrowed and then the plots are measured 
out, each corner being marked by a stake driven well 
into the ground. The fertilizers for each division are 
mixed and applied by hand, care being used not to 
scatter the material beyond the plot, for which it is 
intended. The diagram shows the arrangement of 
the plots and the kind and quantity of fertilizing ma- 
terial to be used on each. 



USING COMMERCIAL FERTILIZERS 227 

The plots may be seeded separately but it saves labur 
and gives practically as good results if the> are planted 
with the remainder of the field. In any case the 
seeder must be run lengthwise of the plots so as to 



No Fertilizer 



15 lbs. Nitrate of Soda 
15 lbs. Sulphate of Potash 
30 lbs. Acid Phosphate 



30 lbs. Acid Phosphate 
15 lbs. Sulphate of Potash 



No Fertilizer 



15 lbs. Nitrate of Soda 
15 lbs. Sulphate of Potash 



15 lbs. Nitrate of Soda 
30 lbs. Acid Phosphate 



No Fertiliser 



avoid dragging any of the fertilizer from one plot to 
another. 

Harvesting the Crop. — The area devoted to the 
experiment should receive exactly the same treatment 
during the growing season as the rest of the field, ex- 
cept that in no case is cross cultivation of the plots 



228 FIRST PRINCIPLES OF SOIL FERTILITY 

allowable. In case of corn, for instance, the cultivator 
could be run lengthwise of the plots but any cultiva- 
tion in the other direction would have to be done with 
the hoe to avoid carrying any of the fertilizers on the 
other plots. In many cases it is not even necessary 
to harvest the crop on the several divisions separately, 
for the difference in the plots is so marked that it will 
be apparent to the eyes. Generally, however, it is de- 
sirable to harvest and determine the yield from each 
plot. If the crop is one which is planted in rows and 
inter-tilled it will be best to harvest the same number 
of rows from the middle of each division, discarding 
the outer rows as well as those on the spaces between 
the plots. In the case of small grains or hay crops, 
the best procedure is as follows : Stretch a cord around 
each plot from stake to stake, now cut away the growth 
for a small space around the experimental area and 
in the intervening spaces. This leaves each plot stand- 
ing out distinctly so it can be readily observed and the 
crop easily harvested. The weight of both grain and 
straw from each plot should be determined. 

Interpreting the Results. — The yield from each of 
the three check plots should be practically the same. If 
this is the case it shows that the soil in the area devoted 
to the experiment is uniform in character. Any great 
difference in the checks invalidates the experiment as 
it then would be impossible to determine if the varia- 
tion in the plots was due to the fertilizer added or to 
a difference in the composition of the soil. A little 
thought will enable one to decide from the experi- 
mental data what elements of fertility gave satisfac- 
tory results with the crop and soil under investigation. 



USING COMMERCIAL FERTILIZERS 229 

If the yield on all the plots, was practically the same, 
for instance, it would be evident that no beneficial 
results could be expected on that soil from the use of 
commercial fertilizers. If plot number 2 gave higher 
results than any of the others it would indicate that 
nitrogen, phosphoric acid and potash were all required. 
If plots 2, 3 and 6 gave larger yields than the checks 
and 5 did not it would suggest that phosphoric acid 
alone was necessary. An increased yield on 2, 3, and 
5 but not on 6 indicates need of potash. A larger crop 
on 2, 5 and 6 but not on 3 shows need of nitrogen. 
A large increase in yield over the checks on 2 and 6 
and a smaller increase on 3 and 5 suggest that both 
nitrogen and phosphoric acid are beneficial but potash 
is not ; and so on. 

In case the person conducting a series of experi- 
ments of this kind feels in doubt regarding the proper 
interpretation of the results, he will find the Agricul- 
tural Colleges and Experiment Stations ready to assist 
him if he will submit his data to them. 

More Extensive Experiments Desirable. — An ex- 
periment such as that described should be conducted 
for several vears in succession in order to obtain very 
reliable data as to the fertilizer requirements of a 
soil. Some peculiarity of climatic conditions or other 
factors might cause variations in yield one year which 
could not be repeated ; hence the result of an experi- 
ment of only one year's duration must be regarded as 
merely suggestive and not final in the answer to the 
questions propounded. The test described includes 
the minimum number of plots, and several more could 
be added to advantage if more comprehensive data are 



230 FIRST PRINCIPLES OF SOIL FERTILITY 

desired. It would be a decided improvement to add 
three plots on which nitrogen, phosphoric acid, or 
potash alone was used. Much useful information could 
also be gained by having additional plots for ( i ) barn- 
yard manure; (2) lime; (3) lime and manure; (4) 
nitrogen, phosphoric acid, potash and lime; (5) floats 




A bird*s-eye view of some fertilizer test plots. Such plot tests are the only 

accurate means of determining; the fertilizer requirements of the soil 

and manure, etc. Some authorities suggest adding 
lime to one end of all the plots but on the whole it 
seems more desirable to have separate plots for the lime 
experiments. Whatever the number of tests, there 
should be a check about every third plot to insure the 
uniformity of the soil in the area used for the experi- 
ment. In many states the Experiment Stations are 
willing to co-operate with the farmer in tests of this 
kind provided he will conduct the experiment care- 
full v, and furnish the station with a complete report. 



USING COMMERCIAL FERTILIZERS 23I 

In any case, the colleg-es and experiment stations are 
always glad to help in planning and carrying out the 
experiments as well as interpreting the results. 

Field Tests Only Reliable. — There cannot be too 
much emphasis placed on the statement that field tests 
are the only means of obtaining reliable information 
regarding the plant food required by a crop on a given 
soil. Chemical analysis of the soil, or the soil water, 
have been- suggested as a means of determining the 
proper fertilizer to use, and from time to time various 
methods of making tests in small pots or baskets have 
been recommended, but as it remains to be demon- 
strated that the results of these tests bear any relation 
to those obtained in the field, no dependence can be 
placed on these methods. The only rational practice 
in the use of commercial fertilizers is one that is based 
on the results of field tests. It does not follow from 
this statement that no profit will result from a less 
intelligent use of fertilizers, but it is certain that a 
definite knowledge of the requirements of the crop, 
and the soil are necessary to obtain the most profitable 
increase in yield. 

Commercial Fertilizers Not AU-Sufficient. — Abso- 
lute dependence should not be placed on commercial 
fertilizers alone to maintain the fertility of the soil. 
Their continued application without the use of any 
other method of improving the soil will eventually re- 
sult in serious injury to its physical condition. Com- 
mercial fertilizers add little or no humus to the soil, 
and to obtain the best results it is absolutely necessary 
to provide humus, either by plowing under green crops 
or by the use of barnyard manure. Numerous experi- 



232 FIRST PRINCIPLES OF SOIL FERTILITY 

ments have shown that commercial fertiUzers give 
much better returns when used in connection with barn- 
yard manure than if used alone, and they are coming 
into use in this manner more and more as the subject 
is more thoroughly investigated. 

It may be said here that commercial fertilizers are 
not merely stimulants as is frequently imagined, but 
that they actually supply plant food, and if rationally 
used will leave the soil more fertile than before their 
use instead of decreasing its fertility, as would happen 
if a mere stimulant were used. On the other hand 
there can be no doubt that as commonly employed the 
effect of commercial fertilizers is to deplete the fertility 
of the soil more completely than would be possible 
without their use. Notwithstanding this fact, commer- 
cial fertilizers have an important place in the rural 
economy, but they should not be used to do the work 
that can be better accomplished by properly husband- 
ing the home resources. 



CHAPTER XXI 

BUYING COMMERCIAL FERTILIZERS 

Fertilizer Laws and Guarantees.— It is impossible 
for the farmer to determine the kind and proportion 
of the different materials entering into the composition 
of a fertilizer by its appearance, weight, smell or any 
physical examination. Formerly all commercial ferti- 
lizers were sold without any guarantee of their com- 
position. The injustice done to the purchaser under 
such a system, has resulted in the passage of laws, in 
most States, which require the manufacturer, or dealer, 
to give the actual amounts of the different constituents 
contained in these products. The manufacturers are 
compelled to guarantee the percentage of nitrogen (or 
ammonia), available phosphoric acid, and potash that 
each brand contains, and usually the composition must 
be stated on each bag or parcel of the fertilizer that 
is offered for sale. The enforcement of this law, and 
the chemical examination of the fertilizers to determine 
if they agree with the guarantee, are entrusted to the 
Experiment Stations in some States, while in others 
they are in the hands of the State Department of Agri- 
culture. The results of the analyses of the various 
brands are published in bulletins for free distribution, 
and these should be generally consulted by the farmers 
using fertilizers. One result of the fertilizer laws has 
been greatly to reduce the number of brands offered 

233 



234 FIRST PRINCIPLES OF SOIL FERTILITY 

for sale, and the decrease has fallen in a great measure 
on the low grade goods, as the worthlessness of a large 
number of such brands has been exposed by chemical 
analysis. 

Guarantees are Often Confusing. — The only con- 
stituents that should be taken into consideration in the 
purchase of a mixed fertilizer are nitrogen (or am- 
monia), available phosphoric acid, and potash. These 
must be stated in the guarantee, and the fertilizer laws 
are so well enforced in most States that the buyer is 
safe in assuming that he will receive the guaranteed 
amount of these three constituents. The laws, how- 
ever, do not prevent the use of other statements on 
the bags. The result is that in many cases superfluous 
words and reiterations are used, apparently with the 
intent of confusing the purchaser. Phosphoric acid 
10 per cent, for instance, is often stated as equivalent 
to bone-phosphate 22 per cent, whether the phos- 
phoric acid actually comes from bone or from rock 
phosphate. The unwary consumer sees the larger 
figure, 22 per cent, and is led to believe that he is 
obtaining something more than the 10 per cent of phos- 
phoric acid which is all that is guaranteed. Potash, 
likewise, is often stated as equivalent to sulphate of 
potash, whether or not the sulphate is used in its man- 
ufacture. The following example taken from the label 
on a brand of fertilizer on the market illustrates this 
point. 

The only point of interest to the buyer in this state- 
ment of analysis is the per cent of nitrogen (or am- 
monia), available phosphoric acid, and potash. In the 
state in which this fertilizer was found on sale, am- 



BUYING COMMERCIAL FERTILIZERS 235 

GUARxVNTEED ANALYSIS 

Per cent. 

Nitrogen 82 to i 

Equivalent to ammonia i to 2 

Available phosphoric acid 8 to 10 

Equivalent to available bone phosphate . . 18 to 22 

Total phosphoric acid 9 to 12 

Equivalent to bone phosphate 25 to 30 

Potash actual 2 to 3 

Equivalent to sulphate of potash . . . . 3-5 to 5 

monia is guaranteed instead of nitrogen. As the dealer 
is held Hable only for the lowest amounts stated in the 
guarantee, ^his statement, when shorn of its redundant 

expressions would read as follows : 

Per cent. 

Ammonia i 

Available phosphoric acid 8 

Potash 2 

Consult the Control Bulletin. — In buying ferti- 
lizers as in the purchase of other commodities it is 
desirable to get the highest possible return for the 
money invested. It has been pointed out that more 
plant food can be obtained for the money in the un- 
mixed basic materials than in any kind of mixed fer- 
tilizers, but in spite of this fact there are undoubtedly 
large numbers of persons who will continue to buy 
mixed goods for years to come. The attention of such 
persons is again called to data given on page 215, show- 
ing the relative cost of plant food in high and low 
Q-rade fertilizers. Whatever form is used the fertilizer 
should be purchased only on the basis of its analysis as 
shown by the bulletin from the control laboratory, or 



236 FIRST PRINCIPLES OF SOIL FERTILITY 

in case this is impossible, on the basis of the lowest 
amounts of nitrogen (or ammonia), phosphoric acid 
and potash which it is guaranteed to contain. In many 
States the bulletins referred to give in addition to the 
analysis the calculated trade value or commercial 
valuation. This in most instances represents what 
would be the actual cost of the amount of the three 
valuable ingredients of the fertilizer, if they were pur- 
chased for their average retail trade price. Where 
such a table is available the farmer will do well to con- 
sult it before making his purchase, and in general terms 
it may be said that he should never pay for a mixed 
fertilizer very much in excess of the price a ton given 
in the commercial valuation. 

Calculating the Commercial Value of a Fertilizer. 
— The purchaser, in the majority of instances, should 
be governed in the price he pays for a fertilizer by the 
valuation placed on it by the control station. In some 
states this valuation is not given, or the prospective 
buyer may not be in possession of the bulletin. In this 
case the commercial value of the fertilizer may be cal- 
culated easily from the guaranteed analysis. First de- 
termine the number of pounds of nitrogen, available 
phosphoric acid, and potash, in a ton of the fertilizer. 
Then multiply by the value a pound (15 cents for nitro- 
gen and 5 cents each for phosphoric acid and potash), 
and the sum of the results so obtained will be the 
retail value of the crude material used in the fertilizer. 
A simple method which will give very nearly the com- 
mercial valuation of a fertilizer is to multiply the per- 
centage of ammonia by two and one-half, add the 
product to the percentages of available phosphoric acid 



BUYING COMMERCIAL FERTILIZERS 237 

and potash, and the rcsuh will be the commercial value 
of a ton of the fertilizer in dollars and cents. 

Example: — The fertilizer mentioned above is guar- 
anteed to contain i per cent of ammonia, 8 per cent of 
available phosphoric acid and 2 per cent of potash. 
Multiplying i by 2.5 gives 2.5. To this add 8 and 2 
and the result is 12.50, which means that the commer- 
cial value of the fertilizer is $12.50 a ton. In case the 
analysis states nitrogen instead of ammonia the nitro- 
gen should be multiplied by 3, and added to the avali- 
able phosphoric acid and potash. The valuation de- 
termined in this way should be compared with the sell- 
ing price of the fertilizer, and the difference should 
never exceed $5 a ton. It is of interest to note that 
the fertilizer mentioned in the example retailed for 
$21 a ton. This is an excess of $8.50 over the cost 
of the crude materials, which is just the average cost 
of mixing, etc., as determined by Voorhees (see page 
216). In calculating the value of the fertilizer the 
buyer must shut his eyes to everything but the lowest 
guaranteed per cent of the three essential ingredients, 
and must not allow himself to be confused by any state- 
ments of equivalents. 

Unit Basis of Purchase. — In commercial transac- 
tions most of the quotations of the crude materials used 
in the manufacture of fertilizers are based on the unit. 
A unit means i per cent on the basis of a ton, or 20 
pounds. For example a unit of available phosphoric 
acid would be 20 pounds, and if the quotation was $1 
a unit the phosphoric acid would cost 5 cents a pound. 
This system is applied to the sale of nitrate of soda, 
the potash salts, blood meal, tankage, superphosphate, 



238 FIRST PRINCIPLES OF SOIL FERTILITY 

etc. In nitrog-enous goods the price is usually stated 
at so much a unit of ammonia. This system, all things 
considered, is the most satisfactory to both purchaser 
and dealer, as the one gets exactly what he pays for, 
and the other is paid for all he delivers. The number 
of units in the material is determined by chemical 
analysis. At the present time this system is rarely used 
in the sale of mixed goods, but there is no reason why 
it should not be applied to these as well as to the un- 
mixed materials. 

Names of Fertilizers Sometimes Misleading. — 
There is no doubt that in many cases an attractive 
name plays an important part in the sale of a ferti- 
lizer. Unfortunately the brand name of a fertilizer is 
not necessarily any indication of its composition. An 
instance in this connection is the abuse of the word, 
bone, by the fertilizer manufacturers. They are fully 
aware that the average farmer favors bone as a source 
of phosphoric acid, and as a consequence that word 
often appears in the brand name when it should not. 
There are licensed in a certain State over 100 fertili- 
zers with the word, bone, occurring in the brand name, 
which either have none of the phosphoric acid derived 
from bone, or have at least a part of the phosphoric 
acid in the form of rock phosphate. Others are called 
humus fertilizers, when they contain practically no 
organic matter, which is the only source of humus. 
These facts emphasize the statement that the buyer 
should carefully study the bulletin from the control 
station, and base his purchase wholly on the cold facts 
therein stated. It may be said in passing that there 
is a movement on in several states to revise the ferti- 



BUYING COMMERCIAL FERTILIZERS 239 

lizer laws so as to compel the maker of fertilizers to 
state the materials entering into the composition of a 
brand, as well as its content of the three essential in- 
gredients. Such a law if possible of enforcement would 
be a distinct advance over the present system. 

Cooperative Buying. — Money can always be saved 
by buying large quantities, for the dealers are justi- 
fied in giving better prices on large lots, and as a rule 
better freight rates can be secured. Where a number 
of farmers in a community are using the same kind of 
goods it will be to their advantage to buy coopera- 
tively through the granges or farmers' clubs. The 
crude materials especially can be bought more cheaply 
in this way. In some places, a certain mixture has 
been found to be satisfactory by a number of farm- 
ers, and they have the goods mixed by a manufacturer 
in accordance with their own specifications calling for 
a certain formula and specific ingredients. This method 
usually gives better results than the indiscriminate pur- 
chase of the so-called standard brands. As a general 
rule it may be said that, taking the precaution to com- 
pare the commercial valuation and the selling price, 
it is always wise to purchase high-grade fertilizers. 

Trade Values not Agricultural Values. — The val- 
ues for commercial fertilizers and manures which have 
been discussed are trade values, and do not necessarily 
bear any relation to the agricultural value of these sub- 
stances. Trade values are determined by the law of 
supply and demand, and many of the materials used in 
commercial fertilizers are required by other industries 
as well, so it is not the agricultural demand alone that 
sets the price. The agricultural value of a fertilizer is 



240 FIRST PRINCIPLES OF SOIL FERTILITY 

measured by the value of the increased crop produced 
by its use, and is, therefore, a variable factor depending 
upon the availability of its constituents, and the char- 
acter of the crop to be raised. It is possible to have 
circumstances under which a fertilizer with a compara- 
tively low commercial valuation may have a high agri- 
cultural value. 

Must Know v^^hat Fertilizer is Needed. — It is not 
sufficient to know how to calculate the commercial 
value of a fertilizer, and to be able to determine if 
the price asked is reasonable. One must also know the 
food requirements of the crop, and the condition of the 
soil before he can intelligently purchase fertilizers. A 
piece of land which was deficient in potash, for in- 
stance, would not be benefited by the use of a fertil- 
izer which contains little or no potash, but which 
might be of great value when used elsewhere. In 
other words, the purchaser who desires to buy that 
which will give him the best returns must be guided 
by chemical analysis even more than by the commercial 
valuation. 

Home Mixing the Most Rational Practice. — The 
idea of mixing the fertilizers on the farm is daily be- 
coming more popular. This is attested by the fact 
that every year a larger number of dealers in fertil- 
izers are offering for sale the unmixed goods. Al- 
ready it has been noted that the plant food can be pur- 
chased at a lower cost in the basic materials, and that 
the form of combination is often as important as the 
actual amounts present. It is only by buying the un- 
mixed goods that one can be certain of the form of 
the plant food. But aside from these considerations 



BUYING COMMERCIAL FERTILIZERS 24I 

there is an educational value in the use of the separate 
ingredients, which is lost when mixed goods are em- 
ployed. This fact has been aptly stated in a bulletin 
from the New York station at Geneva, as follows: 
— "There is little of educational value in using an un- 
known mixture. To purchase intelligently unmixed 
fertilizing materials will ultimately lead in most cases 
to a well grounded knowledge of the science of agri- 
culture. One will seek to know what the dififerent 
forms of plant food are, what they do, from what 
source they can be obtained, and how he can use them 
to best advantage. He will become to some extent an 
investigator and will of necessity take a deeper inter- 
est in his work. His entire system of farming will 
be lifted to a higher plane, and his more intelligent 
labor will yield more profitable results." 



CHAPTER XXII 

INDIRECT FERTILIZERS 

Soil Amendments. — There are a number of sub- 
stances which are beneficial to the land under some 
conditions, although they add neither humus nor im- 
portant quantities of plant food. Such substances have 
been called soil amendments, and the benefit derived 
from their use arises from the fact that they produce 
certain chang-es in the soil, which directly, or indi- 
rectly, promote plant growth. Some of these amend- 
ments contain small amounts of plant food, but their 
value is chiefly due to their secondary effect, and not 
that they add nitrogen, phosphoric acid or potash. 

Lime an Important Indirect Fertilizer. — Lime is 
probably the most important substance of this class, 
and its use as a manure antedates the Christian era. 
Although lime has been employed as a fertilizer for 
so long a time, it is only in recent years that its action 
has been explained, and at the present time there re- 
main for investigation many questions concerning the 
action of lime upon the soil. 

In a few instances lime has a direct manurial value, 
for occasionally a soil is found which is so lacking in 
this substance that the crops are unable to obtain sufifi- 
cient lime for a maximum yield. Such soils are rare, 
and in nearly every instance the good results from the 
use of lime are due to its indirect effect. The effects 
of lime may be considered to be of three kinds, i. c, 
physical, chemical and biological. 
242 



IXnlRECT FERTILIZERS 



243 



Lime Improves Physical Condition of Soil.— Lime 
has a very marked effect on the physical condition of 
the soil ' Wlien added to the sandy soil it tends to 
make the soil more compact by partially cementing 
together the particles of sand, and thus makes the soil 
capable of retaining larger quantities of water. When 




A home-made Hme-kiln for burning Hme. The hmestone was placed on a pile 
of wood and the whole covered with sod and earth 



used on clav lands, on the other hand, lime makes he 
soil more mellow. A clay soil containing very little 
Hme is made fine with greatest difficulty; it adheres 
to the implements used when wet, and cracks when 
allowed to dry. A soil rich in lime crumbles more 
easily, is readily brought into good tilth, and does not 
adhere to any appreciable extent to the implements. 
The addition of lime to a soil containing much clay 
makes the soil more friable, makes it possible for the 



244 FIRST PRINCIPLES OF SOIL FERTILITY 

rains to percolate more easily through the soil, and 
overcomes the danger of puddling. The puddling of 
clay soils is due to the fact that the clay is composed 
of very small granules which fit so closely together 
that the water cannot pass between. When lime is 
added to the soil a number of these small particles 
become cemented together to form a much larger gran- 
ule, and as the granules increase in size the spaces be- 
tween them also become larger. 

Any one can easily satisfy himself in regard to this 
valuable effect of lime on stiff clay by taking a sam- 
ple of such clay, adding a little water, working it thor- 
oughly, and then allowing it to dry, when it becomes 
as hard as a brick. If to another portion of the clay 
a little lime is added (say !]/> per cent.), and this is 
moistened, mixed thoroughly, and allowed to dry, it 
will be found that a mere touch will cause it to crum- 
ble to pieces. There are other materials that have a 
somewhat similar effect en clay, but none arc so effi- 
cient as lime. This granulated condition of clay soils, 
so easily accomplished by liming, is not readily de- 
stroyed but will last for some years. 

Lime Makes Potential Plant Food Available. — 
Lime is useful in making potential plant food avail- 
able. Much of the potash of the soil, for instance, is 
locked up in insoluble compounds, and is not available 
to the plant. Lime may decompose these compounds, 
and thereby convert the potash into forms that the crop 
can use. Experiments have proved that when lime is 
applied to a soil originally poor in this constituent the 
plants grown are not only richer in lime, but also in 
potash. The use of lime, then, may for a time have a 



INDIRECT FERTILIZERS 



245 



similar effect to that of potash-containing manures, but 
it must be remembered that the hme does not supph' 
potash, it merely makes that present in the ground 
available, and if the store of potash originally present 
is small, the soil will probably need liberal potash ma- 




Another home-made lime-kiln lined witli sandstone. Limestone and coal 
are added each day at the top, and the burned lime raked out from the bottom 

nuring at an earlier date because of liming. Caustic 
lime acts energetically upon organic matter, and its 
beneficial action on peaty or other soils containing 
large quantities of undecomposed vegetable matter may 
be partly due to this fact. 

Lime Promotes Grov^th of Desirable Bacteria. — 
Lime is valuable because it promotes the growth of 
desirable bacteria in the soil. It has been shown that 



246 



FIRST PRINCIPLES OF SOIL FERTILITY 



one of the most important changes in the soil due to 
bacterial action is the process of nitrification. The 
nitrifying bacteria cannot thrive in a soil that is defi- 
cient in lime. These bacteria are injured by acidity, 
so it is necessary to keep the soil sweet to promote 
their action. On the other hand, the injurious process 










,-s:i«- 



Beets grown on acid soil. The lot to the left on a plot to which lime was 
added while that on the right was unlimed 

of denitrification takes place more readily in sour soils, 
so that lime in promoting the desirable process over- 
comes the undesirable. The bacteria which grow in 
the nodules found on the roots of the legumes and 
which "fix" the nitrogen of the air will not perform 
their functions in an acid soil, so that lime in keeping 
the soil sweet promotes the gathering of nitrogen by 
the leguminous plants. In general it may be said that 
all the desirable fermentations in the soil are acceler- 
ated by the presence of lime. 

Lime Makes Sour Soil Sweet. — Recent investiga- 
tions have shown that many soils fail to produce good 



INDIRECT FERTILIZERS 247 

crops because they are acid or sour. Formerly it was 
supposed that only low lying or marshy land ever be- 
came sour, but experiments conducted by the Amer- 
ican stations have demonstrated that there are large 
areas of uplands where an acid condition of the soil 
exists. Acidity of the soil is injurious to nearly all 
of the cultivated crops, so that good returns cannot 
be expected from sour lands. Where such a condi- 
tion exists the liberal use of lime is the proper rem- 
edy. Acidity may result from a number of causes 
such as the presence of stagnant water, turning un- 
der large quantities of organic matter, constant use 
of commercial fertilizers, etc., but whatever the cause 
lime is the practical neutralizer. An acid condition of 
the soil can sometimes be foretold by observation of 
the character of the plant growth thereon. Where 
such plants as the common sorrel, beard grass, rushes 
and mosses grow to the exclusion of the more desi- 
rable plants it is a pretty sure indication that the soil 
is acid, for the plants named are not injured by acid- 
ity, while the others are. 

Testing Soil for Acidity. — One of the best methods 
for testing the soil for acidity, is, what is known as, 
the litmus paper test. The test is applied as follows : 
A little of the surface soil is scratched aside and the 
piece of litmus paper pressed on the moist soil beneath. 
If after some time the paper turns a reddish color it 
shows that the soil is sour. To obtain good results, 
only the best neutral litmus paper should be used. 
The directions given for making this test are often 
misleading. One frequently sees such a statement as 
this : "Test with blue litmus paper. This can be bought 



248 FIRST PRINCIPLES OF SOIL FERTILITY 

at a drug store for a few cents," etc. As a matter of 
fact, the blue litmus paper usually found in the retail 
stores is worthless for this purpose. It is not suffi- 
ciently sensitive to acid, and an amount of acid, that 
would prevent the growth of clover entirely might 
not change the color of this common litmus paper at 




Effect of lining acid soils on growth of clover. The large pile on the left 
was grown on the limed plot, the very small pile next to it being weeds. 
The second pile from the right shows the clover, and the pile on the ex- 
treme right the weeds from a plot of the same area which received no lime. 

all. One who contemplates making the test should be 
sure to obtain a sample of extra sensitive neutral lit- 
mus paper, which the druggist can procure for him 
if he does not keep it in stock. 

Clover as an Indicator. — The clovers and other 
leguminous plants require more lime than do the cere- 
als, and are much more sensitive to acidity of the soil. 
A good stand of clover, therefore, is an indication that 
the soil contains sufficient lime. If, on the other hand. 



INDIRECT FERTILIZERS 249 

the clover, after takmg root in the spring, is found later 
in the season to be making no growth, and finally to 
disappear, the indications are that the soil is acid and 
that an application of lime will be beneficial. In a 
great many cases the failure of clover has been shown 
to be due to acidity of the soil. The best way for de- 
termining the need of lime is by means of a plot test 
as described for commercial fertilizers. Soils derived 
from granite, slate or shale are prone to be deficient 
in lime. 

Kind of Lime to Use. — Lime has been used on the 
soil in the various forms of quicklime, hydrated lime, 
slaked lime, marl and ground limestone. If the lime 
is used to improve the physical condition of heavy clay 
soils quicklime is undoubtedly the best form to apply 
to the soil. More often the lime will be used to cor- 
rect acidity, and in this case the best form to use is 
probably that which can be most cheaply obtained and 
applied, keeping in mind the fact that about two tons 
of ground limestone or marl will be required to fur- 
nish as much actual lime as one ton of quicklime. 
Finely ground limestone is apparently coming into 
high favor for correcting the acidity of soils, and where 
it can be obtained at a sufficiently low cost is undoubt- 
edly the safest form to use, especially by the inexpe- 
rienced. In some experiments the ground limestone 
has given better results than quicklime. 

Applying Lime. — As the lime is gradually carried 
downward in the soil it should always be applied to 
the surface, and if possible thoroughly incorporated 
with the few upper inches of the soil. From one-half 
to one and one-half tons of lime an acre (or twice as 



250 FIRST PRINCIPLES OF SOIL FERTILITY 

much ground limestone), applied once in five or six 
years is usually sufficient. Lime cannot be handled in 
the ordinary fertilizer drill, as it packs above the feeder 
and fails to run out evenly, and these drills will not 
apply the lime in sufficient quantity. Satisfactory spe- 
cial lime drills are on the market. Ground limestone 
can be broadcasted from the wagon, but slaked lime 



^ 




W?l 








^;J 




'^S^f...., 


i i M^- iriA^i! 




wmim 


illV 


kWIH 



Applying lime to the soil. The lime drill should be followed by the harrow 

is a disagreeable material to handle in this way. Either 
substance can be applied with an ordinary manure 
spreader by first covering the bottom of the spreader 
with litter to prevent the material from sifting through. 
In any case the lump lime must first be slaked. 

Another way of applying lump lime is to distribute 
the freshly burned lime in small piles over the field, 
throw a little water on the lime and cover with earth. 
After the lime has slaked, mix it with more earth and 
spread with the shovel. Half a peck to the square rod 
would give about 1,400 pounds to the acre. As a gen- 



INDIRECT FERTILIZERS 25 1 

eral rule quicklime should be used only in the autumn, 
while ground limestone may be applied at any time. 
Lime should never be mixed with commercial fertil- 
izers, yet the best results will be obtained from com- 
mercial fertilizers on a soil that is abundantly supplied 
with lime. 

Lime not a Universal Remedy. — So many articles 
are appearing in the agricultural press describing the 
benefits of liming the land that there is some danger 
of exaggerating its importance. No investigations in 
agriculture of recent years have led to better results 
than those on the use of lime, but one must not lose 
sight of the fact that there are many soils which would 
not be at all benefited by the addition of lime, and 
that in some instances the use of lime actually resulted 
in a decreased crop. It must be remembered that lime 
adds no plant food to the soil, but simply brings about 
conditions which enable the crop to use larger quanti- 
ties of the food already present, so that if used alone 
it makes the exhaustion of the soil the more rapid. 
Lime can in no way take the place of good tillage, or 
the use of manure, green manures or fertilizers. 
There is an old saying to the effect that 'lime makes 
the father rich, but the son poor," and this is undoubt- 
edly true if lime is used alone. It has, however, a 
legitimate place in agriculture, and if used in connec- 
tion with green crops, barnyard manure and commer- 
cial fertilizers will in many cases produce beneficial 
results. Lime should never be used immediately be- 
fore a crop of potatoes, as it has a tendency to in- 
crease the scab if the land or seed is infected with the 
scab-producing organism. It is probably best applied 
to clover in the rotation. 



252 FIRST PRINCIPLES OF SOIL FERTILITY 

Marl. — In iiiany places arc found beds of marl of 
considerable size. Most of the marls are formed from 
shell deposits, and consist of carbonate of lime of more 
or less purity. As marl is practically the same as 
ground limestone, it has the same efifect on the soil, 
and is a convenient form in which to use lime when 
obtainable at reasonable cost. Some of the European 
marls contain appreciable quantities of potash and 
phosphoric acid as well, but the American marls are 
of value only for the lime they contain. 

Gypsum or Land-Plaster is a compound of lime 
with sulphuric acid (sulphate of lime) and has been 
used for many years as a fertilizer. For a long time 
the action of land-plaster was little understood, but 
it is now generally believed that its beneficial action 
is due to the fact that the plaster sets free the una- 
vailable potash of the soil, and for this purpose it is 
more useful than lime. It is of value to those crops 
that are benefited by the use of potash manures and, 
as will be surmised, plaster gives good results only on 
soils containing large amounts of potential potash. For 
this reason it gives best returns when used on clay 
soils and practically no beneficial results when used 
on sandy soils. The best method of using it is prob- 
ably to add it to manure as has been suggested. When 
gypsum has been used continually it has been found 
that after a time it fails to produce satisfactory re- 
sults. In the latter case it is probable that the crop 
would be benefited by an application of potash manure. 
Hilgard has found that gypsum is valuable in remov- 
ing the so-called black alkali from the alkali soils of 
western United States. 



INDIRECT FERTILIZERS 253 

Salt of Doubtful Value. — Salt was among- the first 
substances to be used as a manure, but in spite of the 
antiquity of its use the value of salt as a fertilizer is 
still in dispute. It is certain that injury quite as often 
as benefit has resulted from the application of salt. 
In fact, it may be said that there are no experiments 
of any note, which indicate that salt has any benefi- 
cial effect on plant growth. Large quantities of salt 
are poisonous to plants as everyone knows, due un- 
doubtedly to the chlorine that the salt contains. It 
was formerly supposed that such plants as asparagus 
were benefited by the application of salt, but investi- 
gations have not shown any increase in yield from its 
use. It is well known that salt checks fermentations 
of all kinds so that it probably decreases the rate of 
nitrification which is seldom desirable. It is said that 
adding salt to the land will make the straw of wheat 
stiffer, but this effect is very likely due to the fact that 
the salt on account of its poisonous action makes the 
straw shorter and the greater stiffness is due to re- 
duced length. Many so-called agricultural salts are 
on the market, but they certainly do not possess any 
virtues not found in common salt, and it is doubtful 
if there is any manurial value in salt of any kind. 



254 



FIRST PRINCIPLES OF SOIL FERTILITY 



COMPOSITION OF MATERIALS USED IN THE MANUFACTURE 
OF COMMERCIAL FERTILIZERS 



Nitrogen 
per cent 



Phos. Acid Potash 
per cent 1 per cent 



Dried blood — red 

Dried blood— black 

Dried meat meal, or azotine 

Hoof meal 

Dried fish 

Tankage 

I^eather meal 

Sulphate of Ammonia 

Nitrate of Soda 

Raw bone meal 

Steamed bone meal 

Bone black 

Bone ash 

South Carolina rock 

Florida rock 

Tennessee rock 

Basic slag (Thomas phosphate) . . . . 
Acid phosphate or superphosphate . . 

Acidulated bone meal 

Kainit 

Muriate of Potash 

Sulphate of Potash 

I,ow grade sulphate of potash 

Wood ashes 



13-14 

6-12 

13-14 

10-12 

7-8 

4-9 

10-12 

20-21 

15-16 

4-5 

1-2 



6-8 
3-18 



90-24 
25-30 
32-36 



18-30 
25-32 
15-20 
12-16 
12-16 



10-13 

50 

50-53 

26 

4-0 



INDIRECT FERTILIZERS 



255 



COMPOSITION OF FARM MANURES 



Cattle, fresh 

Cattle, rotted (in yard) 

Cattle, deep stall 

Horse, fresh 

Horse, rotted 

Pigs, fresh 

Sheep, fresh 

Sheep, rotted ^in yard) . . . . 
Human excrements mixed . . 

Poultry 

Mixed farm manures, fresh . 
Mixed farm manures, rotted 



^ S 
.« ^ 



73.0 
70.0 
57.0 
73.0 
64.0 
73 
93.5 
56.0 
75.0 
74.0 



^^ 



0.44 
0.32 
0.64 
0.58 
0.44 
0.45 
0.83 
0.63 
0.70 
1 60 
0.45 
0.50 



0.16 
0.14 
0.36 
0.28 
0.35 
0.19 
0.23 
0.81 
0.26 
1.50 
0.21 
0.26 



0.40 

0.47 

0.87 

0.53 

0.49 

0.60 

0.67 

0.44 

0.21 

0.8 

52 

0.63 



256 



FIRST PRINCIPLES OF SOIL FERTILITY 



TERTILIZING CONSTITUENTS OF FARM PRODUCTS AND 
FEEDING STUFFS 



Alfalfa, green plant 

Alfalfa, hay 

Apples 

Artichoke, Jerusalem 

Asparagfus 

Atlas meal (see distillery feed) 

Barley, grain 

Barley, straw 

Barley, green plant 

Barley, malt 

Barley, malt sprouts 

Barley, Brewers' grains (dry) . 
Barley, Brewers' grains (wet) . 

Bean, field, seed 

Bean, field, hay 

Bean, field, straw 

Bean, soy, (see Soy bean) . . . 

Beet, red 

Beet, sugar 

Beet, leaves 

Blackberries 

Bran (see wheat) 

Brewers' grains (see barley) . 
Buckwheat, green plant . . . 

Buckwheat, hay 

Buckwheat, seed 

Butter 



Pounds in moo 



Div 
Mailer 



Nitro- 



249 
925.3 
158.0 
200.0 
63 7 



857.0 
858.0 
313 7 
925.0 
880.0 
905 



857.0 
840 
81G.0 



122.7 
180 
110.0 
110.9 



163.0 
840.0 
867.0 
920 9 



6.8 
22.4 
0.95 
2.6 
30 

15 1 
5.5 
3.3 
16.0 
37 
33 
8.1 
40.7 
29.6 
13.0 

24 

2.1 



4.0 

7.7 

17 

1.2 



Phos. 
Acid 



1.4 
5.1 
0.2 
1.4 

0.8 



2.0 
2.0 
9.3 
17.4 
16.1 
4.2 
12 
6.4 
2.7 

0.9 

0.8 
0.0 
0.9 



0.7 
6.1 



INDIRECT FERTILIZERS 



257 



FERTILIZING CONSTITUENTS— CONTINUED 



Pounds in 1000 



Buttermilk 

Cabbage 

Carrots 

Cauliflower 

Cheese 

Cherries 

Clover, (medium red), green plant 

Clover, hay 

Clover, seed 

Clover, straw 

Clover, (mammoth , hay 

Clover, (crimson), green 

Clover, (crimson), hay 

Clover, (alsike), green 

Clover, (alsike\ hay 

Corn, grain, (flint) 

Corn, grain, (dent) 

Corn, bran 

Corn, cobs . . . . 

Corn and cob meal 

Corn, green plant 

Corn fodder with ears 

Corn fodder without ears 

Corn, silage 

Corn by-products : 

Germ meal 

Gluten feed 

Gluten meal 



Dry 
Matter 



Nttro- 
o-en 



98.8 
110.0 
130.0 
93.9 
667 5 
157.0 I 
210.0 1 
842.0 I 
850 ; 
845.0 ; 
886 
185 
836.0 
182.0 
840.0 
879.0 
882 
909.0 
875.3 
910 4 
2m7.0 
921.5 
908 8 
220 5 

896 
922 
914.0 



64 
2.4 

2.0 
2.6 
39.3 

1.8 
5.4 
20.7 
30.5 
14.7 
22 3 
4.5 
19 1 
4.7 
21 6 
16.6 
16 2 
16.3 
4.2 
14.1 
2 9 
17.6 
10 4 
2.8 

26.5 

38 4 
50 3 



Phos. 
Acid 



2.2 

1.4 
0.9 
1.6 
6.0 
0.6 

1.5 

5.6 
14.5 

42 

5 5 

1.2 

3.8 

1.0 

5.0 

57 
12.1 
0.4 
5.7 
1.2 
5.4 
2.9 
1 1 

80 
4.1 
3.3 



Potash 



2.6 

3.6 

1.2 

20 

4.8 
18.9 
13.5 
12.6 
12.2 

40 

12.4 

2 1 
13.9 

3.7 

3 7 
6.8 
4.1 
4.7 
40 
89 

14 
37 

5.0 
03 
05 



258 



FIRST PRINCIPLES OF SOIL FERTILITY 



FERTILIZING CONSTITUENTS CONTINUED 



Cottonseed meal 

Cow-peas, green plant . . . 

Cow-peas, hay , 

Cream 

Cucumbers 

Distillery feed (Atlas) ... 

Eggs 

Flax seed 

Germ meal (see corn) . . , , 
Gluten meal (see corn) . . 

Grapes , 

Hops, whole plant . . . . , 

Hops, flowers , 

Kentucky Blue-grass .... 

Kohl-rabi , 

I^ettuce 

lyinseed meal (see oil meal) 

Maize (see corn) 

Malt, etc. (see barley) ... 
Mangel-wurzel (mangolds) 
Meadow hay (mixed) . . . , 
Middlings (see wheat) . . . , 

Milk 

Milk, skim 

Millet, green plant 

Millet, hay 

Oats, green plant 

Oats, grain 



Pounds in looo 



Dry 
Matter 



911.8 
211.9 
893.0 
259.5 
42 1 
887.9 
328.0 
923.0 



170.0 
860.0 
880.0 
896.5 
119.6 
60.1 



127.1 
863.0 



128 3 
95.7 
374.0 
902.0 
166.4 
867.0 



Nitro- 
gen. 



69 

2.7 

26.6 

40 

1.6 

53.0 

2! 8 

38 3 



Phos. 
Acid 



1 6 
25.0 
32.2 
11.9 
4.8 
2.2 



1.9 
14.7 



5.1 
5.2 
6.1 

12 8 
4.9 

16.5 



3.0 
1.0 
5.2 
1.5 
1.2 
2.3 
3.7 
20.3 



1.1 

5.8 
11.1 
4.0 

2.7 
0.8 



0.9 
4.1 



1.9 
2.1 
1.9 
4.9 
1.3 
6.9 



INDIRECT FERTILIZERS 



259 



FERTILIZING CONSTITUENTS CONTINUED 



Oats, hay 

Oats, straw 

Oil meal (old process) . 
Oil meal (new process) 

Onions 

Orchard grass, green . 
Orchard grass, hay . . 

Parsnips 

Peaches 

Peanut cake meal . . . 

Pears 

Peas (field), green plant 

Peas, hay 

Peas, seed 

Peas, straw 

Plums 

Potatoes, common . . . 

Potatoes, sweet 

Pumpkin 

Radish . 

Rape 

Red-top hay 

Ruta-bagas 

Rye, grain 

Rye, green plant .... 

Rye, straw 

Rye-grass hay 

Sainfoin hay 



Pounds in 1000 



Drv 

Matter 



Nitro- 
gen 



885.0 
855.0 
910.6 
890.0 
132.2 
300.0 
889.0 
168.0 
1210 
896.0 
164.9 
181.0 
850.0 
860.0 
864.0 
343.0 
250.0 
2G6.0 
192.0 
67.0 
145.0 
917.0 
109.0 
857.0 
234.0 
864 
880.0 
845.0 



11.9 
4.6 

53.2 

56.4 
2.0 
3.8 

13.0 
1.8 
1 

75.6 
0.7 
5.4 

19.4 

36.0 

14.3 
1.8 
34 
2.3 
1.1 
1.9 
4.5 

12 
19 

17 6 
5.3 
4.9 
20.8 
2i.2 



Phos. 
Acid 



16.4 
17.4 
0.8 
1.3 
3.8 
2.0 
0.5 
13.1 
0.4 
1 5 
2.7 
8.4 
3.5 
0.3 
1.6 
0.9 
1.6 
0.5 
1.5 
3.6 
12 
8.5 
25 
25 
7.6 
46 



Potash 

25.4 

17.7 

13.1 

13.4 

1.7 

5.9 

17.7 

4.4 

2.4 

15 

1,3 

5.1 

6.3 

10.1 

10.2 

2.0 

5.7 

4.1 

0.9 

1.6 

3.6 

10.2 

4.9 

5.8 

7.1 

8.6 

24.6 

13.2 



26o 



FIRST PRINCIPLES OF SOIL FERTILITY 



FERTILIZING CONSTITUENTS CONTINUED 



Serradella hay , 

Sorghum seed 

Sorghum, green plant . . 

Soy beans, hay , 

Soy beans, seed 

Soy beans, straw 

Spinach 

Strawberries 

Sugar beets (see beets) . . 
Timothy, green plant . . 

Timothy, haj^ 

Tobacco, leaves 

Tobacco, stalks 

Tobacco, stems 

Tomatoes 

Turnips 

Vetch (hairy), green plant 

Vetch, hay 

Vetch, seed 

Vetch, straw 

Wheat, bran 

Wheat, grain 

Wheat, green plant . . . 
Wheat, middlings .... 

Wheat, shorts 

Wheat, straw 

Whey 



Pounds 



Dry 
Matter 



870.0 
866.0 
178.0 
937.0 
900.0 
840.0 
80 4 
94 8 



331.0 

863 
820.0 
938.0 
820.0 
63.6 
92.0 
175.0 
840.0 
840.0 
850.0 
883.0 
866 
233.0 
874.0 
882.0 
857.0 
66.2 



Nitro- 
gen 



24.3 

14.6 

2.3 

23.2 

53.6 

11.8 

4.9 

1.5 



48 

9.7 

24.5 

37.0 

25.0 

1.6 

1.9 

5.1 

36.8 

37 

10 9 

20.7 

19.3 

5.4 

22.8 

28.2 

48 

1.4 



Phos. 
Acid 



8.4 
8.1 
09 
6.7 
14,5 
2.9 
1.0 
0.8 



5.0 
6.6 
65 
9.3 
0.5 
0.9 
1.2 
9.7 



1.5 
13.5 
13.5 



INDEX 



PAGE 

Abandoned farms .... 4 

Acidity, effect of lime on . . 247 

effect on clever .... 248 

testing soil for . . . .247 

Acid phosphate 203 

Agriculture an art ... 3 
Air necessary to roots . . 65 

Alluvial soils 56 

Ammonia, sulphate of . . . 192 

Ammonite 190 

Animal charcoal .... 202 
Assimilation of carbon . . 17 
Atmosphere as source of plant 

food 12 

Available phosphoric acid . . 204 
Available plant food . . .45 
Azotin 190 

Barley grown continuously . 7 
Barnyard manure, see manure. 

Blood, dried 190 

Bone-black 202 

Bone-meal 201 

Capillarity, experiments to 

show 81 

Carbon comes from air . . 17 
costs farmer nothing . . 20 
amount of in air . . . 19 
Carbonic acid . . .17, 18,67 
Catch crops for green-manur- 
ing 102 

Chemical analysis of soil . . 45 



Chili saltpeter . 
Chloroohyll .... 
Commercial fertilizers 

all made from a few 
terials .... 

buying commercial fertiliz 
ers 

calculating value of . 

cheap fertilizers expensive 

consult bulletin 

cooperative buying . 

field tests with 

guarantees misleading . 

high grade .... 

home mixed . . . 21 

low grade 

mixed 

names misleading 

nitrogeneous materials . 

not all sufficient . 

should not take place of ti 
lage 

unit basis of purchase . 



PAGE 
193 

17 
2-241 



188 

233 
236 
214 
235 
239 
225 
234 
213 
240 
213 
209 
238 
190 
231 

186 
237 



using commercial fertilizers 219 

what they are .... 188 

Complete fertilizers . . .209 

Composition of corn plant 9-11 

Composts 162, 164 

Covered barnyards save ma- 
nure 158, 161 

Crop indicates fertilizer needed 224 



Deep stall manure . 



161 



261 



262 



FIRST PRINCIPLES OF SOIL FERTILITY 



PAGE 

Denitrification . . . . 24, 40 

prevented by tillage ... 66 

Drainage 75 

beneficial on high lands . 81 

increases available water . 79 

warms soil 11 

Drift soils 57 

Early spring plowing ... 72 

Earth mulch 70 

Elements and compounds . 8 
Essential elements . . . .32 
Exhaustion of the soil . . 6 
how to prevent . . . . 59 
Expensiveness of cheap ferti- 
lizers 214 

Exposed manure, how to care 

for 162 

Fallows, short desirable . . 92 
Farming a business ... 3 
Feeding stuffs, composition of 117 
Fertile soils must contain ni- 
trogen 50 

Fertility, effect of style of 

farming on .... 179 
removed by crops . . 42, 43 
Fertilizers applied to money 

crops 223 

Field experiment, conducting 

experiment 226 

harvesting crop .... 227 
interpreting results . . . 228 

only reliable 231 

should be extensive . . . 229 

with fertilizers .... 225 

First plants simple organisms 51 

Fish guano 191 

Fixation of carbon . . .17 
Floats with manure . . . 207 
Freezing water, effect of . 48,51 



PAGE 

Function of different food ele- 
ments 37 

Glaciers in soil formation . 47 

Green manuring . . . 94, 99 

catch crops for .... 102 

danger from 102 

not advisable on stock farms 103 
two classes of plants for . 100 
Green plants use carbonic acid 17 
Growing crop prevenlr, loss of 

nitrogen 89 

Gypsum 252 



High grade fertilizers . 
Home mixed fertilizers 
Hoof meal .... 
Horn meal .... 



213 
215 
190 
191 



Hot fermentation should be 

prevented 156 

How mineral matter enters 

plant 

Humus 

a store house of plant food 

decreased by tillage . 

increases soil water . 

increased by green manur- 
ing 

important in soil formation 

improves physical condition 
of soil .... 

makes mineral food availa 
ble 



Igneous rocks 47 

Incompleted soil .... 65 

Indirect fertilizers . . . 242 

Inoculation of soil .... 28 

Irrigation 75 

effect on yield .... 84 
in humid climates experi- 
mental 82 



35 
94 
97 
98 
95 

99 
52 

96 

98 



INDEX 



263 



PAGE 

Kainite 199 

Land-plaster 252 

Late fall plowing . . . . 71 
Leaching of manure removes 

available nitrogen . . 146 

Leather meal 192 

Legumes, fixation of nitrogen 

by 26, 28 

in soil formation .... 53 

nodules on roots of . 26, 28 

Lichens on rocks .... 54 

Lime 242 

applying to soil .... 249 
corrects acidity .... 246 
effect on clover .... 248 
improves physical condition 243 

kind to use 249 

makes food available . . 244 
makes sour soil sweet . • 246 
not a cure-all . . . .251 
promotes growth of desira- 
ble bacteria .... 245 
Liquid excrement, composition 

of 138 

plant food more available in 

139, 140 
value of ..... . 127 

Litmus test 247 

Loss of plant food by leach- 
ing, etc. ..... 38 

Low^ grade fertilizers . . . 213 
Lysimeter to show loss of ni- 
trogen 87 

Manure, amount and value 

from different animals 115, 116 

amount of plant food re- 
moved in 120 

amount produced on farm 127 



PAGE 

Manure, applying . . . .165 
as a crop producer . . .173 
best used when fresh . .153 
calculatmg amount of 123, 126 
compared with fertilizers . 174 
composition of . . 114,115 

composting 162 

depth to cover .... 167 
effect of bedding on value 123 
effect of ration on value per 

ton 122 

factors affecting value of . 113 
fresh and rotted compared 169 
from fifty cows . . 127, 133 
how to increase value of . 134 
importance of . . . .113 
lasting effect of . . . .175 
losses in, from fermentation 146 
losses in, from leaching 141, 144 
nitrogen most valuable con- 
stituent of 

no loss with matured ani- 
mals 

relation to fertility . 
should be protected 
weather .... 
the best fertilizer 
value of determined by 

tion 

value little appreciated 

Manuring grass lands 

Marl 

Meat meal .... 

Milk contains plant food 

Mineral constituents of 

Mineral phosphates 

Mixed fertilizers 

Moss growing on granite 

Movement of soils 

Muriate of potash . 



pl 



ra 



mt 



121 



118 
177 



154 
176 



117 
127 
168 

252 

190 

118 

31 

202 

209 

51 

55, 56 

. 199 



264 



FIRST PRINCIPLES OF SOIL FERTILITY 



PAGE 

Nature's method contrasted 

with man's 57 



Nitrate of soda 


. 193 


Nitrification . . . . 


22,23 


Nitrification, hastened by 


til- 


lace 


. 66 


Nitrogen as plant food . 


. 21 


comes from soil . 


. 21 


expensive 


. 196 


fertilizers, availability of 


. 193 


fixation of 


24,28 


in soil, source of 


. 22 


most costly food 


. 21 


of air, can plants use? . 


. 24 


Nodules on legumes 


26,28 



Open yard feeding wasteful 146 

Origin of soil 47 

Osmosis 36 

Oxygen from the air . . 16 

Peruvian guano .... 192 
Phosphate materials . . .201 
Phosphates, relative value of 204 
Physical condition of soil im- 
portant 45 

Plant food, amount of in soil 44 
Plant removes something from 

soil 8 

Plants differ in food require- 
ments 105 

in manner of growth . . 106 

of first importance ... S 

Plot tests with fertilizers . 225 

Plowing 63, 71, 72 

Potash and soda on spinach 34 
Potash fertilizers . . . .197 
comparison of .... 200 
Potential plant food ... 46 
Preservation of manure . .150 
Primary soils 47 



PAGE 

Pulverization of rocks . . 48 

of soil beneficial ... 64 

Reverted phosphoric acid . . 204 

Root hairs 35 

Roots in soil formation . . 52 
Rothamsted experiments . 7, 25 
Rotation, controls diseases, in- 
sects and weeds . . .107 
economizes labor .... 107 
effect on yield . . . .108 

improves soil 107 

planning a 109 

origin of 105 

Rock phosphate 203 

Running water, effect of 2, 49 

Salt 252 

Sedentary soils 56 

Selective power of plants . . 36 
Soil solutions very dilute . . 36 
Solid excrement, composition 

of 138 

losses from leaching , . 144 

value of 127 

Soy beans, nodules on roots 

of 28,29 

Small part of plant food from 

soil 40 

Special fertilizers .... 210 
Spring plowing, conserves 

moisture 72 

Stable manure, on corn . .112 

Stassfurt salts 199 

Summer fallowing, adds noth- 
ing to soil 86 

King's experiments on . .90 
may cause loss of nitrogen 88 

origin of 85 

Sulphate of potash . . . .199 
Superphosphates .... 203 
Sunlight necessary to carbon 

fixation 18 



INDEX 



265 



Surface washing, loss of food 

by 39 

Tankage 191,202 

Tillage, aerates soil ... 66 

aids nitrification .... 66 

conserves moisture . . 62, 69 

destroys weeds . . . . T^ 

hastens chemical changes . 65 

increases available water . 68 

increases feeding ground . 63 

prevents denitrification . . 66 

Transpired water .... 12 

Transported soils .... 56 

Tubercles on roots of legumes 

26,28 



Unit basis of purchase 

Various agencies concerned in 

soil formation . 
Ville system .... 



PAGE 

237 



Wagner system 
Water, functions of 

importance of, to plant . 

required by crop, amount 
of 13,14 

table ....... ^6 

Weathering of limestone . . 52 
Weeds, destroyed by tillage . 73 
Wheat grown continuously . 7 
Wood ashes 1^8 



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